Sen. Hillary Rodham Clinton said recent anti-Jewish comments by the president of Iran show the pressing need to address that country's nuclear ambitions.
Iranian President Mahmoud Ahmadinejad said in a televised speech Wednesday that the Holocaust was "a myth," sparking immediate condemnation from the White House and European leaders.
The former first lady wrote to Secretary of State Condoleezza Rice on Thursday denouncing the Iranian leader's speech as "outrageous and disgusting."
Ahmadinejad has stepped up his anti-Israel rhetoric since October when he called for Israel to be "wiped off the map."
In her letter, Clinton said, "To deny the Holocaust places the President of Iran in company with the most despicable bigots and historical revisionists."
She urged the US to take a tough line on Iran, particularly given international concerns about their budding nuclear program.