Iranian President Mahmoud Ahmadinejad has written a letter to President Bush proposing "new ways" to resolve their differences, an Iranian government spokesman says.

In the letter -- believed to be the first from an Iranian leader to an American president in 27 years -- Ahmadinejad proposes "new ways for exiting from the current critical situation," Gholam-Hossein Elham said Monday.

Elham, quoted by the state-run television and radio network IRIB, said Ahmadinejad had "analyzed the current international condition and has pointed out the way to find the root causes."

The letter -- which does not directly mention the contentious issue of Iran's nuclear ambitions -- was sent to Bush through the Swiss Embassy in Tehran, Elham said.

Aneesh Raman, CNN's correspondent in Tehran, said the letter is expected to arrive at the White House on Monday.

"The specifics of the letter will not be made public until Bush receives the letter," Raman said.

The key question is whether the letter will lead to any "direct talks" between Iran and the United States, he added.

According to the state-run news agency IRNA, Ahmadinejad told reporters he had decided to send letters to leaders of certain countries on the occasion of "Year of Great Prophet Mohammad."

It is believed to be the first correspondence between the presidents of Iran and the United States since 1980, when Washington broke off ties with Tehran over the hostage crisis.

The announcement came just ahead of a meeting of the five permanent members of the U.N. Security Council in New York.