President Obama on Tuesday denied floating any "quid pro quo" with Russia over junking a missile defense shield Moscow opposes in exchange for Russia's help in stopping Iran from building nuclear weapons.

The president said that his recent letter to Moscow expressed his stance that reducing the threat of a nuclear Iran in turn reduces the need for a missile defense shield in Eastern Europe. 

Senior U.S. administration officials previously suggested there was a trade-off in the letter, which they said hinted that plans for the defense shield could be unnecessary if Russian President Dmitry Medvedev helped in blocking Iran's progress toward building long-range missiles. 

But Obama walked that claim back in a session with reporters following his meeting Tuesday with British Prime Minister Gordon Brown

"It was simply a statement of fact that I've made previously," he said, stressing that the defense shield would be aimed at Iran, not Russia. 

"And what I said in the letter was 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 said he has made clear that the U.S. needs to "reset or reboot" its relationship with Russia.

The Kremlin also disputed talk of any trade-off in the letter. In Moscow, a Kremlin source told FOX News there was no quid pro quo on Iran and missile defense in the letter, but said the correspondence was considered very positive and contained a number of initiatives. 

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. 

A senior administration official told FOX News that the U.S. will continue to "consult with Poles and Czechs as we move forward with decisions on missile defense." 

Obama and Medvedev were expected to meet at the G-20 economic summit of advanced and developing nations in London next month, according to the officials. The administration has previously hinted that the policy on the missile defense shield that former President George W. Bush fiercely advocated was open to reassessment. 

On Monday, Russian Foreign Minister Sergey Lavrov urged the United States to restore diplomatic relations with Iran, Russian news agencies reported. "This would be an important element in stabilizing the situation in the region," he said. 

Lavrov is scheduled to hold talks with Secretary of State Hillary Rodham Clinton in Geneva on Friday in the highest-level meeting between the two nations since Obama took office. 

At a February gathering of NATO defense chiefs in Krakow, Poland, Defense Secretary Robert Gates said that Washington would review the missile plan "in the context of our relationship with both Poland and the Czech Republic" as well as with NATO and Russia. The language marked a departure from the tone of the Bush administration, which enthusiastically promoted the plan and signed deals last year with Warsaw and Prague. 

Gates said that if Moscow really wants to stop the missile shield, it should help eliminate the threat of a missile attack from Iran. 

The Obama administration has been vocal about its desire to repair rifts between the U.S. and Russia. In Munich last month, Vice President Joe Biden told a gathering of world leaders, "It's time to press the reset button and to revisit the many areas where we can and should be working together with Russia." 

The Associated Press contributed to this report.