The White House warned Republican Senators on Saturday that legislation requiring that Congress approve any deal reached with Iran over its nuclear capabilities could have a "profoundly negative impact" on negotiations.
The warning in a letter from White House Chief of Staff Dennis McDonough, sent days before the due date for a framework of a deal that would limit Iran's nuclear capabilities, is the latest sign of rising tension between the White House and Republicans in Congress over the negotiations.
Republicans who oppose the negotiations say lifting sanctions on Iran could enable its development of a nuclear weapon and have proposed legislation that would require Congressional approval of any deal.
The White House previously said President Barack Obama would veto the proposed legislation.
This week, 47 Senate Republicans sent a letter to Iran warning that any deal reached could be overturned by the next U.S. president.
McDonough said Congress will ultimately have the power to lift or continue sanctions on Iran, but that any legislation requiring they approve the deal could be damaging to the talks.
"We believe that the legislation would likely have a profoundly negative impact on the ongoing negotiations - emboldening hard-liners, inviting a counter-productive response from the Iranian majiles; differentiating the U.S. position from our allies in the negotiations; and once again calling into question our ability to negotiate this deal," McDonough wrote.