In a letter to President Barack Obama, 29 leading American scientists expressed support for the nuclear accord reached last month between six world powers and Iran.

The two-page letter, sent Saturday, is intended to boost the White House’s position as it battles to win over at least one-third of either chamber of the US Congress to prevent a veto-proof “no” vote on the deal by skeptical lawmakers.

The deal is “technically sound, stringent and innovative,” with “more stringent constraints than any previously negotiated nonproliferation framework,” claim the signatories, some of whom worked in senior government posts related to security and nuclear policy.

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The nuclear deal offers Iran dramatic easing of biting international sanctions in exchange for increased limits and tightened international monitoring of its nuclear program. Critics, including Israeli officials and many US lawmakers, insist it will not, at the end of the day, prevent Tehran from pursuing a nuclear weapons capability.

The letter briefly addresses critics: “Some have expressed concern that the deal will free Iran to develop nuclear weapons without constraint after ten years. In contrast we find that the deal includes important long-term verification procedures that last until 2040, and others that last indefinitely under the NPT [Non-Proliferation Treaty] and its Additional Protocol.”

The first signature is that of Richard Garwin, a key designer of the first hydrogen bomb described by The New York Times as “among the last living physicists who helped usher in the nuclear age.” Five of the signatories are Nobel laureates in physics: Leon Cooper, Sheldon Glashow, David Gross, Burton Richter and Frank Wilczek.

Stanford professor Siegfried Hecker, a former director of the Los Alamos laboratory where American nuclear weapons are designed, also signed the letter. Princeton physicist Freeman Dyson, famous for his research into quantum mechanics and astronomy, is another signatory, as is former congressman and physicist Rush Holt, Jr.

The letter offers an outline of the agreement’s limits on the Iranian nuclear program, which it says would leave Iran “many months” away from enriching enough uranium for a nuclear weapon, and praises its “innovative approaches to verification.”

The deal “limits the level of enrichment of the uranium that Iran can produce, the amount of enriched uranium it can stockpile, and the number and kinds of centrifuges it can develop and operate. The agreement bans reconversion and reprocessing of reactor fuel, it requires Iran to redesign its Arak research reactor to produce far less plutonium than the original design, and specifies that spent fuel must be shipped out of the country without the plutonium being separated and before any significant quantity can be accumulated,” it explains.

It “will advance the cause of peace and security in the Middle East and can serve as a guidepost for future nonproliferation agreements,” the scientists write.