Forty-seven Republican senators warned on Monday that any agreement the Obama administration strikes with Iran to limit Tehran’s nuclear programme may be short-lived unless Congress approves the deal. The White House accused the Republicans of advocating a “rush to war”.

In an open letter to Iranian leaders, freshman Senator Tom Cotton and 46 other Republicans said that without congressional approval any deal between Iran and the US 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 US and other countries 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.

Though the Republican letter was addressed to leaders in Tehran, it seemed as much aimed at delivering a message in the United States.

Republicans and some Democrats want Congress to vote on any agreement. The pact the bargainers are working on would not require congressional approval because it is not a treaty. A treaty would require a two-thirds majority Senate vote to be ratified.

Dick Durbin, the No 2 Democrat in the Senate, accused the Republicans of risking another war in the Middle East.

“This is a cynical effort by Republican senators to undermine sensitive international negotiations. It weakens America’s hand and highlights our political divisions to the rest of the world,” Durbin said in statement. “Understand that if these negotiations fail, a military response to Iran developing their nuclear capability becomes more likely. These Republican senators should think twice about whether their political stunt is worth the threat of another war in the Middle East.”

Last week, the Republican Senate majority leader, Mitch McConnell, postponed action on legislation to give Congress a vote on any deal that emerges. He delayed the measure in the face of solid Democratic opposition to moving ahead on the bill now, just weeks before an end-of-March deadline for negotiators to produce an outline of an agreement.

The letter released on Monday was signed by 47 of the Senate’s 54 Republicans. Included were McConnell and the rest of the Senate leadership plus presidential contenders Marco Rubio, Rand Paul and Ted Cruz.

Missing from the letter were seven Republicans, including Senator Bob Corker, the chairman of the foreign relations committee.