Obama has written a confidential letter to Russian counterpart Dmitry Medvedev about the link between the US plans to deploy a missile defense system in Europe and Iranian ambitions, a senior US official confirmed.

"President Obama sent a letter to Medvedev covering a broad range of topics, including missile defense and how it relates to the Iranian threat," the White House official told AFP on condition of anonymity.

The official offered no further details of the secret letter, or when it was sent.

But The New York Times said it was delivered three weeks ago to Moscow by "top administration officials" and was intended to give Russia an incentive to forge a common front with the United States to quell any threat from Iran.

The US could rethink its plans to site a missile defense shield in eastern Europe, which have been strongly opposed by Russia, by contending such a defense system was no longer necessary in exchange for Moscow's help with Iran, the Times said.

The overture was rebuffed Tuesday by Medvedev, who said it was "not productive" to link talks over the US missile defense system with Iran's suspected nuclear program.

"If we are to speak about some sort of exchange, the question has not been presented in such a way, because it is not productive," Medvedev said during a trip to Spain Tuesday.

But he acknowledged: "Our American partners are ready to discuss this problem. This is already good."

US officials, under the previous administration of president George W. Bush, have long said the shield to be based in the Czech Republic and Poland aimed to counter the threat of long-range missiles from such countries as Iran.

The Times stressed the letter did not offer a specific quid pro quo.

"It's almost saying to them, put up or shut up," a senior official was quoted as saying by the influential daily.

"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."

Asked about it in Jerusalem, US Secretary of State Hillary Clinton said the missile defense system "has always been intended to deter any missile that might come from Iran."

"That's been our stated position. It remains our position. We have explained that to the Russians before," she said, adding she would discuss the issue at length with Russian Foreign Minister Sergei Lavrov when the two meet for talks in Geneva on Friday.

Moscow, which enjoys close links to Tehran, has been angered for years by Bush's plans to place interceptor missiles in Poland and a powerful radar in the Czech Republic, saying the move was directly aimed against Russia.

Bush officials said the system was intended to protect Europe and the United States against a limited long range missile attack by Iran, which Washington accuses of trying to develop nuclear weapons.

On Monday, Iran again denied that it is seeking to produce a nuclear bomb, after top US military commander Admiral Mike Mullen charged that it has enough fissile material to build such a weapon.

"All this talk is baseless," foreign ministry spokesman Hassan Ghashghavi said at his weekly news conference.

Iran has rejected repeated calls by the UN Security Council -- of which Russia is a permanent member -- to halt uranium enrichment, despite three sets of UN sanctions for its defiance. The Islamic republic says its nuclear program is merely for peaceful domestic energy purposes.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.