A group of 47 Republican senators has warned in an open letter that any nuclear deal between U.S. President Barack Obama's administration and Iran may be short-lived unless it obtains congressional approval.
The Obama adminsitration and Iran's foreign minster criticized the senators for the unusual move, which U.S. officials said could undermine tough negotiations between six powers and Tehran weeks ahead of a deadline for a landmark deal on its nuclear program.
In the letter, to Iranian leaders, Senator Tom Cotton and 46 other Republicans said that without such approval, any deal would be just an agreement between Obama and Iran's supreme leader, Ayatollah Ali Khamenei.
The letter said, "The next president could revoke such an executive agreement with the stroke of a pen and future Congresses could modify the terms of the agreement at any time."
Republicans and some Democrats want Congress to vote on any agreement.
The White House denounced efforts by Republican lawmakers to "throw sand in the gears" of talks over Iran's nuclear program.
White House spokesman Josh Earnest called the letter a "continuation of a partisan strategy" to undermine Obama's foreign policy strategy.
Earnest said the letter "certainly interferes" in efforts to negotiate a deal with Tehran.
Obama said it was "somewhat ironic to see some members of Congress wanting to make common cause with the hard-liners in Iran. It's an unusual coalition."
The Senate's number-two Democrat, Richard Durbin, called the letter "a cynical effort" to undermine sensitive international negotiations.
Iranian Foreign Minister Mohammad Javad Zarif dismissed the letter as a "propaganda ploy" and noted that many international deals are "mere executive agreements."
"I wish to enlighten the authors that if the next administration revokes any agreement 'with the stroke of a pen'...it will have simply committed a blatant violation of international law," he said in a statement.
Washington and five other powers are seeking a pact that would restrict Iran's nuclear program, easing fears Tehran could develop atomic weapons, in exchange for sanctions relief. They have set a March 31 target for a political framework and a June 30 deadline for a full deal.
The pact the negotiators are working on does not require congressional approval because it is not a treaty, which would require a two-thirds majority Senate vote to be ratified.
Zarif last week said that the validity of any deal would have to be guaranteed by a vote in the UN Security Council.
With additional reporting by Reuters, AP, and politico.com