The Arms Control Association, a nonpartisan group based in Washington, will release the statement Tuesday morning. It declares the deal limiting Iran’s nuclear program in return for sanctions relief “a net-plus for international nuclear nonproliferation efforts.”

Among the 75 signatories are the former CIA agent Valerie Plame and her husband, Joe Wilson, prominent opponents of the Iraq War. Others include Hans Blix, a former director of the International Atomic Energy Agency (IAEA); Morton Halperin, a foreign policy veteran of three administrations; and Thomas Pickering, a retired diplomat and former U.S. ambassador to Israel.

Several former United Nations disarmament officials, along with leaders of think tanks and foundations dedicated to preventing the spread of nuclear arms, also added their names. Some of the signatories are already known supporters of the deal, which was struck in July.

Their message amplifies a core argument of the Obama administration: that the nuclear deal is well built and durable, and exceeds historical standards for arms control agreements.

If fulfilled by all parties, the statement says, the agreement “will reduce the risk of a destabilizing nuclear competition in a troubled region… and head off a catastrophic military conflict over Iran’s nuclear program.”

Amid a political uproar in Washington, the deal has mostly been celebrated by technical experts. Earlier this month, 29 prominent scientists wrote to Obama saying the deal has “more stringent constraints than any previously negotiated nonproliferation framework.”

But many critics of the deal, led by Republicans in Congress and Israeli officials, argue that it is filled with dangerous loopholes and concessions. They have focused, for instance, on a provision that could theoretically allow Iran to stall for up to 24 days before IAEA inspectors can examine a suspicious undeclared site.

The Arms Control Association statement argues that the deal’s monitoring and verification provisions “make it very likely that any future effort by Iran to pursue nuclear weapons, even a clandestine program, would be detected promptly, providing the opportunity to intervene decisively to prevent Iran from acquiring a nuclear weapon.”

The statement does not directly address a larger concern of opponents — that once the deal’s core provisions sunset after 15 years, Tehran will be poised to install advanced centrifuges and build a weapon in a matter of weeks.

It notes that “all of us could find ways to improve the text” of the deal, while adding that “[we] see no realistic prospect for a better nuclear agreement.”

Backers of the nuclear deal are countering a fierce and well-funded lobbying campaign against the accord by groups like the American Israel Public Affairs Committee, which will reportedly spend $40 million on the fight.

Congress is expected to vote on the nuclear deal by Sept. 17 and will almost certainly disapprove it, thereby barring President Obama from suspending sanctions on Iran. But it’s not clear that opponents can muster the two-thirds majority in both the House and the Senate necessary to override a guaranteed Obama veto.

Obama insists that a defeat in Congress will bring down the deal and put America on a path toward war with Iran. Also lobbying Congress for support are America’s five negotiating partners: Great Britain, France, Germany, Russia and China.

Although the White House has suffered setbacks in the Senate — Democratic Sen. Chuck Schumer and Republican Sen. Jeff Flake, a possible swing vote, have both announced their opposition in recent days — it appears for now that Obama can retain enough House Democratic votes to protect the deal.