WASHINGTON (AFP) - US Secretary of State John Kerry hit out Wednesday at a letter by Republican senators to Iran against the nuclear talks he is leading, saying it threatened global trust in America.
"This risks undermining the confidence that foreign governments in thousands of important agreements commit to," Kerry told US lawmakers.
"It purports to tell the world that if you want to have any confidence in your dealings with America they have to negotiate with 535 members of Congress," Kerry added, saying such a notion was "both untrue and profoundly a bad suggestion".
A total of 47 Senate Republicans made the unprecedented move of directly and publicly addressing Iran's leaders in a bid to scupper talks between Western powers and the Islamic Republic over the country's disputed nuclear programme.
In their letter, the Republicans warned that any deal agreed before US President Barack Obama leaves office in 2017 is "nothing more than an executive agreement" that could be struck down by Congress at a later date.
But Kerry, who spent 29 years in the Senate, said the letter's basic premise was untrue, expressing "utter disbelief" at the missive, which comes as the negotiations reach a critical end stage.
"No one is questioning anybody's right to dissent. Any senator can go to the floor any day and raise any of the questions that were raised in that," Kerry said.
But "this letter ignores more than two centuries of precedent in the conduct of American foreign policy," he added.
While formal treaties require the advice and consent of the US Senate, the "vast majority of international arrangements and agreements do not," the US Secretary of State insisted.
The Republican-led Congress has been pushing to be given a vote on any deal reached between global powers - Britain, China, France, Germany, Russia and the United States - and Iran.
But the administration of President Barack Obama has insisted it will be agreed through the President's executive powers, although at some point Congress will have to vote on whether to lift a network of sanctions imposed on the Islamic Republic.
Kerry said that from the "earliest period of American history," both parties in Congress had accepted the President's executive agreement as a "necessary tool" of US foreign policy.
"We've been clear from the beginning that we're not negotiating 'a legally binding plan,'" Kerry said, stressing that Washington and Teheran did not even have diplomatic relations.
"We're negotiating a plan that will have in it the capacity for enforcement."
