"We've already given our response," National Security Council spokesman Frederick Jones said, referring to various statements by Secretary of State Condoleezza Rice and other US officials rejecting Monday's letter from the Iranian leader.

Rice said Monday that the letter that broke 27 years of official and hostile silence between leaders of the two governments contained no proposals for resolving the confrontation over Iran's nuclear ambition.

"This letter is not the place that one would find an opening to engage on the nuclear issue or anything of the sort. It isn't addressing the issues that we're dealing with in a concrete way....It is most assuredly not a proposal," Rice said.

White House spokesman Scott McClellan also said that the letter "doesn't appear to do anything to address the concerns of the international community."

Iranian President Mahmoud Ahmadinejad wrote a letter to U.S. President George W. Bush on finding new solutions to their differences, Iranian government spokesman Gholam Hossein Elham said on Monday.

The letter was delivered to U.S. President George W. Bush by the Swiss embassy to Iran, Elham said.