WASHINGTON (AP) -- Forty-seven Republican senators warned on Monday that any agreement the Obama administration strikes with Iran to limit Tehran's nuclear program may be short-lived unless Congress approves the deal. The White House accused the GOP of advocating a "rush to war."

In an open letter to Iranian leaders, freshman Sen. Tom Cotton of Arkansas and 46 other Republicans said that without congressional approval any deal between Iran and the U.S. would be merely an agreement between President Barack Obama and Iran's supreme leader, Ayatollah Ali Khamenei.

"The next president could revoke such an executive agreement with the stroke of a pen," they wrote, "and future Congresses could modify the terms of the agreement at any time."

The U.S. and other nations are seeking a pact that would let Western powers verify that Iran will not obtain a nuclear weapon.

At the White House, spokesman Josh Earnest said the Republican letter interferes with negotiations over limiting Tehran's nuclear ambitions.

"I would describe this letter as the continuation of a partisan strategy to undermine the president's ability to conduct foreign policy and advance our national security interests around the globe," Earnest said. "The rush to war or at least the rush to the military option that many Republicans are advocating is not at all in the best interest of the United States."

Earnest said the talks with Iran are no different from the negotiations that resulted in an agreement with Syria to eliminate its chemical weapons arsenal. Earnest noted that Congress did not have to approve that agreement.

With Cotton presiding over the Senate at the start of Monday's session, Democratic leader Harry Reid assailed the GOP for undermining the commander in chief and labeled the effort politically motivated.