Obama has offered the deal in a secret letter that was hand-delivered to Russia's President Dmitri Medvedev in Moscow three weeks back, The New York Times quoted unnamed senior American officials as saying.

In fact, the letter states the US wouldn't need to proceed with the interceptor system, which has been vehemently opposed by Russia since it's proposed by Bush administration, if Iran halted any efforts to build nuke warheads as well as long-range ballistic missiles.

"It's almost saying to them, put up or shut up. It's not that the Russians get to say, 'We'll try and therefore you have to suspend.' It says the threat has to go away," said a senior Obama administration official.

And, among other things, the letter discussed talks to extend a strategic arms treaty which is expiring this year and cooperation in opening supply routes to Afghanistan.

Though Moscow has not yet responded officially, a Russian official said that Foreign Minister Sergey V. Lavrov would have something to say on missile defense to US Secretary of State Hillary Clinton [Images] when they meet on Friday in Geneva.

Meanwhile, in an interview posted on the Kremlin website, the Russian President said: "We've already received such signals from our American colleagues."

A couple of weeks back, US Defense Secretary Robert M. Gates had said: "I told the Russians a year ago that if there were no Iranian missile programme, there would be no need for the missile sites."