Washington (AFP) - More than two dozen top US scientists, among them nuclear researchers and Nobel prize winners, praised the Iran nuclear deal as major security achievement in a letter to President Barack Obama, The New York Times reported.The two-page letter, from some of the world's most knowledgeable nuclear experts, could prove to be a shot in the arm for Obama, who has launched a major effort to sell the deals to skeptical members of the US Congress.The letter tells the US president that the Iran deal "will advance the cause of peace and security in the Middle East and can serve as a guidepost for future nonproliferation agreements."The Iran accord, the scientists said, has "more stringent constraints than any previously negotiated nonproliferation framework."There were 29 signatories of the letter in all, some of whom are physicists who have held top level military security clearances.