Iran is calling on the United Nations to stop the United States from making what Tehran perceives as threats of a military attack against its nuclear program.

In a letter Monday to Secretary-General Kofi Annan, Iran's U.N. ambassador, Javad Zarif, urged Mr. Annan and the U.N. Security Council to take action against what it called Washington's illegal threats against Iran.

Zarif quoted President Bush as saying all options are on the table in response to a reporter's question on April 18 on whether the U.S. may launch a nuclear strike on Iran.

Meanwhile, President Bush telephoned his Russian counterpart, Vladimir Putin, to discuss the standoff over Iran's nuclear program. A White House spokesman declined to give details but said the two leaders stressed the importance of preventing Iran from obtaining nuclear weapons.

The spokesman also said they will remain in close contact on the issue.

Russia and China, both permanent U.N. Security Council members, are opposed to a U.N. resolution requiring Iran to stop uranium enrichment or face possible sanctions. They prefer resolving the standoff through talks.

Iran maintains its nuclear program is to create energy. But the United States and other countries accuse it of trying to develop a nuclear weapon.

Some information for this report provided by AP, AFP and Reuters.