The Obama administration has reacted furiously to an open letter to Iran from Republican senators aimed at derailing nuclear negotiations. The White House accused them of seeking to circumvent the constitution and trigger a “rush to war”.

Iran’s foreign minister, Mohammad Javad Zarif, also poured derision on the Republican letter in a statement expressing astonishment that members of Congress would seek to undermine a US administration by writing directly to a foreign power, and suggesting that the letter’s authors had much to learn about international and even US law.

However, the sharpest reaction to Monday’s open letter came from the White House. President Obama accused its 47 Republican signatories of “wanting to make common cause with the hardliners in Iran”.

The US vice-president, Joseph Biden, said the letter, drafted by Tom Cotton, a freshman senator from Arkansas, was “expressly designed to undercut a sitting president in the midst of sensitive international negotiations”.

It was “beneath the dignity of the institution I revere”, Biden said in a statement.

The letter was published as the 18-month-long negotiations on the future scope of Iran’s nuclear programme approach a deadline at the end of this month for a framework agreement. The document, signed by all but seven of the Republican Senate majority, suggests that the Iranian leadership does not understand America’s constitutional complexities and warns that any agreement signed with the Obama administration could be overturned “with the stroke of a pen” by the president’s successor.

Biden said the Republicans’ constitutional argument was “as false as it is dangerous”. He said the “vast majority” of America’s international commitments through the nation’s history had taken effect without congressional approval, adding that the nuclear agreement, if signed, would also be a commitment to the other parties to the talks: the UK, France, Germany, Russia and China.

“In 36 years in the United States Senate, I cannot recall another instance in which senators wrote directly to advise another country – much less a longtime foreign adversary – that the president does not have the constitutional authority to reach a meaningful understanding with them,” Biden wrote.

Many commentators noted that the letter, like the Republican invitation to the Israeli prime minister, Binyamin Netanyahu, to address Congress last week without consulting the White House, marked a dramatic break from the tradition that partisan politics should “stop at the water’s edge” and not spread into critical US defence and security policy abroad.

The White House spokesman, Josh Earnest, portrayed Republican tactics as dangerously reckless. “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,” he said.

The New York Daily News went much further in denouncing the Republicans’ direct communication with a geopolitical adversary at the height of negotiations. It published photographs of some of the signatories on its front page, over the headline: “Traitors”.

Among the seven Republican dissenters who did not sign the Cotton letter was the chairman of the Senate foreign relations committee, Bob Corker, who noted that its signatories were only Republicans, and that he was focused on gathering a bi-partisan two-thirds majority aimed at forcing Obama to submit any nuclear deal to Congress.

Zarif, like President Hassan Rouhani and several other senior members of the Iranian government, holds an advanced degree from a western university, and appears to have taken umbrage at the condescending tone of the senators’ letter. He delivered his own lecture in response.

“I wish to enlighten the authors that if the next administration revokes any agreement with the stroke of a pen, as they boast, it will have simply committed a blatant violation of international law,” he wrote.

It is as yet unclear what effect, if any, the letter and its fallout could have on the seven-party nuclear talks that are due to reconvene in Switzerland on Sunday.

According to deadline laid down by foreign ministers, the negotiations are supposed to produce a framework agreement by the end of March, including the main parameters of the issues in dispute, like Iran’s uranium enrichment capacity and the lifting of western sanctions. Diplomats then have until the end of June to fill the intricate details essential to making any agreement work.