Former secretary of State Hillary Rodham Clinton harshly criticized Senate Republicans for their open letter warning Iranian officials that any nuclear deal reached with President Obama may be only temporary.

The recent letter from Republican senators was out of step with the best traditions of American leadership. And one has to ask, what was the purpose of this letter?" Clinton said Tuesday.

Clinton joined a chorus of senior Democrats in condemning the letter. Vice President Biden, a former senator, said the move was "beneath the dignity of an institution I revere" and "threatens to undermine the ability of any future American President, whether Democrat or Republican, to negotiate with other nations on behalf of the United States."