As the controversy over the Iran deal heats up—and it’s going to get a lot hotter, especially come September—more than 100 former U.S. ambassadors have signed on to a letter drafted by The Iran Project applauding what they characterized as a “landmark agreement” and urging its support by Congress. Signatories included former Under Secretary of State Nicholas Burns, Daniel Kurtzer (ambassador to Israel and Egypt), one-time neoconservative heartthrob Ryan Crocker (ambassador to Afghanistan, Iraq, Pakistan, and Syria), Frank Wisner (former ambassador to India, Egypt, the Philippines, and Zambia and under secretary of defense for international security affairs), and Thomas Pickering (former under secretary of state for political affairs and ambassador to Israel, Russia, India, and the United Nations). The letter was released on the same day that former Secretary of State Madeleine Albright also spoke out in favor of the deal.

Here is the letter and the list of signatories:

Dear Mr. President:

The Joint Comprehensive Plan of Action (JCPOA) with Iran stands as a landmark agreement in deterring the proliferation of nuclear weapons. If properly implemented, this comprehensive and rigorously negotiated agreement can be an effective instrument in arresting Iran’s nuclear program and preventing the spread of nuclear weapons in the volatile and vitally important region of the Middle East. Without your determination and the admirable work of Secretary of State Kerry and his team, this agreement would never have been reached.

As former American diplomats, we have devoted much of our lives to ensuring that the President had available the best possible diplomatic approaches to dealing with challenges to our nation’s security, even while recognizing that a strong military is essential to help the President and the Congress to carry out their duties to protect the nation and its people. Effective diplomacy backed by credible defense will be critically important now, during the period of inspection and verification of Iran’s compliance with the agreement.

The JCPOA touches on some of America’s most important national objectives: non proliferation and the security of our friends in the Middle East particularly Israel. Ensuring the cooperation and implementation of this agreement by a hostile nation will require constant, dedicated U.S. leadership and unflagging attention.

We recognize that the JCPOA is not a perfect or risk-free settlement of this problem. However, we believe without it, the risks to the security of the United States and our friends and allies would be far greater. We are satisfied that the JCPOA will put in place a set of constraints and inspections that can assure that Iran’s nuclear program during the terms of the agreement will remain only for peaceful purposes and that no part of Iran is exempt from inspection. As with any negotiated settlement, the most durable and effective agreement is one that all sides will commit to and benefit from over the long term.

We support close Congressional involvement in the oversight, monitoring and enforcement of this agreement. Congress must be a full partner in its implementation and must evaluate carefully the value and feasibility of any alternative that would claim better to protect U.S. security and more effectively to prevent Iran from acquiring a nuclear weapon. In particular, Congress must give careful attention to evaluating whether alternatives would be more or less likely to narrow the options for resolving this issue without the use of force.

In our judgment the JCPOA deserves Congressional support and the opportunity to show it can work. We firmly believe that the most effective way to protect U.S. national security, and that of our allies and friends is to ensure that tough-minded diplomacy has a chance to succeed before considering other more costly and risky alternatives.

With respect,

Amb. (ret.) Diego C. Asencio, Ambassador to Colombia and Brazil

Amb. (ret.) Adrian Basora, Ambassador to Czechoslovakia

J. Brian Atwood, Administrator of USAID and Under Secretary of State for Management

Amb. (ret.) William M. Bellamy, Ambassador to Kenya

Amb. (ret.) John R. Beyrle, Ambassador to Russia and Bulgaria

Amb. (ret.) James Keough Bishop, Ambassador to Niger, Liberia and Somalia

Amb. (ret.) Barbara K. Bodine, Ambassador to Yemen

Amb. (ret.) Avis Bohlen, Assistant Secretary for Arms Control

Amb. (ret.) Eric J. Boswell, Assistant Secretary of State for Diplomatic Security

Amb. (ret.) Stephen Bosworth, Ambassador to the Republic of Korea

Amb. (ret.) Richard Boucher, Assistant Secretary of State for South and Central Asia

Amb. (ret.) Kenneth C. Brill, Ambassador to the IAEA, UN and founder of the U.S. National Counterproliferation Center

Amb (ret.) Kenneth L. Brown, Ambassador to Republic of Congo, Cote d’Ivoire, and Ghana

Amb. (ret.) A. Peter Burleigh, Ambassador and Deputy Permanent Representative to the United Nations

Amb. (ret.) Nicholas Burns, Undersecretary of State for Political Affairs, Ambassador to Greece and NATO

Amb. (ret.) James F. Collins, Ambassador to the Russian Federation and Ambassador at Large for the New Independent States

Amb. (ret.) Edwin G. Corr, Ambassador to Peru, Bolivia and El Salvador

Amb. (ret.) William Courtney, Commissioner, Bilateral Consultative Commission to implement the Threshold Test Ban Treaty

Amb. (ret.) Ryan Crocker, Ambassador to Afghanistan, Iraq, Pakistan, Syria, Kuwait, and Lebanon

Amb. (ret.) James B. Cunningham, Ambassador to Israel, Afghanistan and the United Nations

Amb. (ret.) Walter L. Cutler, Ambassador to Saudi Arabia, Tunisia

Amb. (ret.) Ruth A. Davis, Ambassador to the Republic of Benin and Director General of the Foreign Service

Amb. (ret.) John Gunther Dean, Ambassador to India

Amb. (ret.) Shaun Donnelly, Ambassador to Sri Lanka

Amb. (ret.) Harriet L. Elam-Thomas, Ambassador to Senegal

Amb. (ret.) Theodore L. Eliot Jr., Ambassador to Afghanistan

Amb. (ret.) Nancy Ely-Raphel, Ambassador to Slovenia

Amb. (ret.) Chas W. Freeman, Jr., Assistant Secretary of Defense and Ambassador to Saudi Arabia

Amb. (ret.) Robert Gallucci, Ambassador at Large

Amb. (ret.) Robert S. Gelbard, President’s Special Representative for the Balkans

David C. Gompert, former Acting Director of National Intelligence

Amb. (ret.) James E. Goodby, Special Representative of the President for Nuclear Security and Dismantlement, and Ambassador to Finland

Amb. (ret.) Marc Grossman, Under Secretary of State for Political Affairs and Ambassador to Turkey

Amb. (ret.) Brandon Grove, Director Foreign Service Institute

Amb. (ret.)William Harrop, Ambassador to Israel, Guinea, Kenya, and Seychelles

Amb. (ret.) Ulric Haynes, Jr. Ambassador to Algeria

Amb. (ret.) Donald Hays, Ambassador to the United Nations

Amb. (ret.) Heather M. Hodges, Ambassador to Ecuador and Moldova

Amb. (ret.) Karl Hofmann, Ambassador to Togo

Amb. (ret.) Thomas C. Hubbard, Ambassador to the Republic of Korea

Amb. (ret.) Vicki Huddleston, Ambassador to Mali and Madagascar

Thomas L. Hughes, former Assistant Secetary of State for Intelligence and Research

Amb. (ret.) Dennis Jett, Ambassador to Mozambique and Peru

Amb. (ret.) Beth Jones, Assistant Secretary of State for Europe and Eurasia

Amb. (ret.) James R. Jones, Ambassador to Mexico and formerly Member of Congress and White House Chief of Staff

Amb. (ret.) Theodore Kattouf, Ambassador to Syria and United Arab Emirates

Amb. (ret.) Richard D. Kauzlarich, Ambassador to Azerbaijan, Bosnia and Herzegovina

Amb. (ret.) Kenton W. Keith, Ambassador to Qatar

Amb. (ret.) Roger Kirk, Ambassador to Romania and Somalia

Amb. (ret.) John C. Kornblum, Ambassador to Germany and U.S. Assistant Secretary of State for European Affairs

Amb. (ret.) Eleni Kounalakis, Ambassador to Hungary

Amb. (ret.) Daniel Kurtzer, Ambassador to Israel and Egypt

Amb. (ret.) Bruce Laingen, Chargé d’Affaires in Tehran (1979)

Frank E. Loy, Under Secretary of State for Global Affairs

Amb. (ret.) William Luers, Ambassador to Czechoslovakia and Venezuela

Amb. (ret.) Princeton N. Lyman, Assistant Secretary of State for International Organization Affairs

Amb. (ret.) John F. Maisto, Ambassador to Organization of American States, Venezuela, Nicaragua

Amb. (ret.) Jack Matlock, Ambassador to the Soviet Union, Czechoslovakia, and Special Assistant to the President for National Security

Amb. (ret.) Donald F. McHenry, United States Permanent Representative to the United Nations

Amb. (ret.) Thomas E. McNamara, Assistant Secretary of State for Political-Military Affairs, Ambassador to Colombia, and at Large for Counterterrorism

Amb. (ret.) William B. Milam, Ambassador to Pakistan and Bangladesh

Amb. (ret.) Tom Miller, Ambassador to Greece and Bosnia-Herzegovina

Amb. (ret.) George E. Moose, Assistant Secretary of State for African Affairs, Ambassador to Benin, Senegal

Amb. (ret.) Cameron Munter, Ambassador to Pakistan and Serbia

Amb. (ret.) Richard Murphy, Assistant Secretary of State for Near Eastern and South Asian Affairs and Ambassador to Saudi Arabia

Amb. (ret.) Ronald E. Neumann, Ambassador to Afghanistan, Algeria, and Bahrain

Amb. (ret.) Thomas M. T. Niles, Assistant Secretary of State for Europe and Canada and Ambassador to Greece

Phyllis E. Oakley, Assistant Secretary, Bureau of Intelligence and Research

Amb. (ret.) W. Robert Pearson, Ambassador to Turkey

Amb. (ret.) Robert H. Pelletreau, Assistant Secretary of State for Near East Affair

Amb. (ret.) Pete Peterson, Ambassador to Vietnam

Amb. (ret.) Thomas Pickering, Undersecretary of State for Political Affairs, Ambassador to Israel, Russia, India, United Nations, El Salvador, Nigeria and Jordan

Amb. (ret.) Joan M. Plaisted, Ambassador to the Republic of the Marshall Islands and Kitibati

Amb. (ret.) Nicholas Platt, Ambassador to Pakistan, Philippines, and Zambia

Amb. (ret.) Anthony Quainton, Assistant Secretary of State for Diplomatic security or Director General of the Foreign Service

Amb. (ret.) Robin L. Raphel, Assistant Secretary of State for South Asia

Amb. (ret.) Charles A. Ray, Ambassador to Zimbabwe and Deputy Assistant Secretary of Defense for POW/Missing Personnel Affairs

Amb (ret.) Arlene Render, Ambassador to The Gambia, Zambia and Cote d’Ivoire

Amb. (ret.) Julissa Reynoso, Ambassador to Uruguay

Amb. (ret.) Francis J. Ricciardone, Ambassador to Egypt, Turkey, the Philippines, and Palau

Amb. (ret.) Rozanne L. Ridgway, Assistant Secretary for Europe and Canada and Counselor of the Department

Amb. (ret.) Peter F. Romero, Assistant Secretary of State

Amb. (ret.) Theodore Sedgwick, Ambassador to Slovakia

Amb. (ret.) J. Stapleton Roy, Ambassador to China and Indonesia

Amb. (ret.) William A. Rugh, Ambassador to Yemen and the United Arab Emirates

Amb. (ret.) Janet A Sanderson, Ambassador to Algeria and Haiti

Amb. (ret.) Teresita C. Schaffer, Ambassador to Sri Lanka

Amb. (ret.) Howard B. Schaffer, Ambassador to Bangladesh

Amb. (ret.) Raymond G. H. Seitz, Ambassador to the United Kingdom

Amb. (ret.) John Shattuck, Ambassador to the Czech Republic

Amb. (ret.) Ronald I. Spiers, Ambassador to Pakistan, Turkey and Assistant Secretary for Politico-Military Affairs

Amb. (ret.) William Lacy Swing, Ambassador to South Africa, Nigeria, Haiti, Congo-DRC, Liberia, and Republic of Congo

Amb. (ret.) Patrick Nickolas Theros, Ambassador to the State of Qatar

Arturo A. Valenzuela, Assistant Secretary of State for Western Hemisphere Affairs and Special Assistant to the President for National Security Affairs

Amb. (ret.) William J. Vanden Heuvel, Deputy Permanent United States Representative to the United Nations

Amb. (ret.) Nicholas A. Veliotes, Assistant Secretary of State for Near Eastern and South Asian Affairs

Amb. (ret.) Richard N. Viets, Ambassador to Jordan

Amb. (ret.) Edward S. Walker, Jr., Ambassador to Israel, Egypt and United Arab Emirates

Amb. (ret.) Alexander F. Watson, Assistant Secretary of State for Western Hemisphere Affairs, and Ambassador to Peru

Amb. (ret.) Melissa Wells, Ambassador to Estonia, DRC-Congo, Mozambique, Guinea Bissau

Amb. (ret.) Philip C. Wilcox Junior, Ambassador at Large for Counter Terrorism

Molly K. Williamson, Deputy Assistant Secretary of State, Defense, and Commerce

Amb. (ret.) Frank Wisner, Ambassador to India, Egypt, the Philippines and Zambia, and Under Secretary of State for International Security Affairs

Amb. (ret.) John Wolf, Assistant Secretary for Nonproliferation

Amb. (ret.) Kenneth Yalowitz, Ambassador to Belarus and Georgia