U.S. President Barack Obama said on Tuesday he wanted to work with Russia to resolve a nuclear stand-off with Iran but denied reports he had offered to slow deployment of a missile defense shield in exchange for Moscow''s help.

The New York Times reported that Obama had sent a letter to Russian President Dmitry Medvedev suggesting he would back off deploying a system in eastern Europe to intercept and destroy missiles, a move Russia sees as a military threat, if Moscow helped stop Iran from developing long-range weapons.

"What I said in the letter is what I have said publicly, which is that the missile defense that we have talked about deploying is directed toward, not Russia, but Iran," Obama said after meeting British Prime Minister Gordon Brown.

"And what I said ... was that, obviously, to the extent that we are lessening Iran''s commitment to nuclear weapons, then that reduces the pressure for, or the need for a missile defense system," he said.

Obama''s defense secretary, Robert Gates, said Washington wanted to reopen dialogue with Moscow on Iran. There were two options, he said -- to work together to persuade Iran not to go ahead with their ballistic missile program, or make Russia a "full partner" in the defense shield.

White House spokesman Robert Gibbs stressed the linkage between the missile shield and Iran at a White House briefing.

"If working with our allies and working with Russia we can eliminate the threat, then you eliminate the driving force behind that system to combat that threat.”