U.S. President Barack Obama says there is room for another arms control deal with Russia.

After talks with Russian President Dmitry Medvedev at the Seoul nuclear summit Monday, Mr. Obama said both countries can continue to make progress in cutting stockpiles of nuclear weapons.

Mr. Obama called the START agreement with Russia ratified in 2010 the most comprehensive arms treaty in 20 years. He said he plans to pursue another round of cuts with Russian President-elect Vladimir Putin.

In an exchange picked up on an open microphone, the U.S. leader said he would have more flexibility to deal with the issue of missile defense after the upcoming U.S. presidential election. Mr. Medvedev said he understood, and would pass the message on to President-elect Putin.

The two leaders apparently did not intend for the remarks to be made public. The White House later released a statement saying that since 2012 is an election year in both countries, it is not a time in which a breakthrough could be expected.

Differences also remain between the United States and Russia on Syria. Despite the disagreements, President Medvedev said relations with Washington are their best in 10 years.