More flexibility after elections

Outgoing Russian President Dmitry Medvedev said he would pass on Obama's message to his successor, Vladimir Putin, according to an audio recording of comments the two leaders made during a meeting in Seoul, South Korea. Obama and Medvedev did not intend for their comments to be made public AP reported.

Once they were, the White House said Obama's words reflected the reality that domestic political concerns in the both the U.S. and Russia this year would make it difficult to fully address their long-standing differences over the contentious issue of missile defense.

Obama, should he win re-election, would not have to face voters again.

"Since 2012 is an election year in both countries, with an election and leadership transition in Russia and an election in the United States, it is clearly not a year in which we are going to achieve a breakthrough," White House deputy national security adviser Ben Rhodes said.

Tensions over missile defense have threatened to upend the overall thawing of relations between the U.S. and Russia in recent years.

Both leaders acknowledged as much in their public statements to reporters following their meeting. Obama said there was "more work to do" to bridge their differences; Medvedev said each country had their own positions on missile defense, but there was still time to find a solution.

Russia has been strongly critical of plans for U.S.-led NATO missile defense in Europe. Russian officials believe the planned missile shield would target Russia's nuclear deterrent and undermine global stability, while the U.S. insists the planned missile shield is intended to counter threats from Iran.

Putin said earlier this month that Washington's refusal to offer Moscow written guarantees that its missile defense system would not be aimed against Russia deepened its concerns.

Putin won elections held earlier this year and will return to the presidency later this spring. He is expected to name Medvedev prime minister.

The U.S. and Russia have also clashed recently over their approach to dealing with violence in Syria. The U.S. has sharply criticized Russia for opposing U.N. Security Council action calling on Syria's president to leave power.

Obama said Monday that despite past differences on Syria, he and Medvedev agreed they both support U.N. envoy Kofi Annan's efforts to end the violence in Syria and move the country towards a "legitimate" government.