President Barack Obama has written to Russian President Dmitry Medvedev suggesting U.S. plans for a missile defense system in Eastern Europe might be unnecessary if Moscow helped in blocking Iran's progress toward building long-range missiles, senior administration officials said on Tuesday.

Plans for deploying U.S. missile defenses in Poland and the Czech Republic, ostensibly to guard against Iranian attacks on U.S. allies in Europe, are among a host of issues that soured U.S.-Russia relations during the former Bush administration. There have been indications Obama, who has vowed to shake up American foreign policy, might be willing to set aside the missile defense system.

Medvedev said he had talked with Obama over the phone and exchanged letters with him, but added that there was "no talk about some kind of trade-off, or quid pro quo."

"No, issues haven't been put that way, it would be unproductive," he said at a news conference Tuesday, which followed talks in Madrid with Spanish Prime Mini