President Barack Obama on Monday sharply criticized an open letter by 47 Senate Republicans warning Iran’s leaders that any agreement between the White House and Tehran on nuclear weapons could be quickly nullified or changed once Mr. Obama leaves office. The lawmakers were effectively aligning themselves with Iranian hardliners who oppose an international nuclear deal, Mr. Obama said. The letter, which was signed by Senate Majority Leader Mitch McConnell (R., Ky.) and a number of top committee chairmen, came as a major new complication in a debate over international nuclear talks that face a March 31 deadline. Senators said that, unless approved by Congress, any agreement between world powers and Iran would be seen by GOP lawmakers as an executive agreement between […]