SEOUL—U.S. President Barack Obama told Russian President Dmitry Medvedev on Monday that his re-election campaign has tied his hands in resolving differences with Russia over U.S. plans for a missile-defense system in Europe, and suggested an agreement would be more likely after November.

President Barack Obama speaks with Russian President Dmitry Medvedev during their meeting in Seoul Monday.
."This is my last election, and after my election I'll have more flexibility," Mr. Obama said to Mr. Medvedev after a meeting in Seoul, according to audio picked up by television cameras that apparently wasn't intended to be heard by reporters.

"I understand," Mr. Medvedev replied.

"I transmit this information to Vladimir," he added, referring to incoming Russian President Vladimir Putin.

The White House confirmed that the exchange came after a discussion about the missile-defense shield, saying in a statement that the issue, which has strained U.S.-Russia relations, won't be resolved before Americans vote in November.

Mr. Medvedev said on Friday that Russia was unconvinced that a planned U.S.-led missile defense shield in Europe is meant to deter an attack by countries such as Iran.

Following Mr. Obama's remarks, the Associated Press reported that Mitt Romney, the leading Republican contender to face Mr. Obama in the U.S. presidential election this fall, said in a statement that the president's unguarded remarks "signaled that he's going to cave to Russia on missile defense, but the American people have a right to know where else he plans to be 'flexible' in a second term."

Mr. Romney, a former Massachusetts governor who often faces charges of having been flexible on his own policies over the years, said Mr. Obama "needs to level with the American public about his real agenda," the news agency said.

Rep. Mike Turner of Ohio, Republican chairman of the House Armed Services Subcommittee on Strategic Forces, wrote to the president requesting an "urgent explanation of [his] comments to President Medvedev," AP reported.

"Congress has made exquisitely clear to your administration and to other nations that it will block all attempts to weaken U.S. missile defenses," Mr. Turner said. "As the chairman of the Strategic Forces Subcommittee, which authorizes U.S. missile defense and nuclear weapons policy, I want to make perfectly clear that my colleagues and I will not allow any attempts to trade missile defense of the United States to Russia or any other country."

A senior White House security official agreed Monday that a breakthrough on the European missile issue shouldn't be expected this year. "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," Ben Rhodes, a U.S. deputy national-security adviser, said in a statement.

"Therefore, President Obama and President Medvedev agreed that it was best to instruct our technical experts to do the work of better understanding our respective positions, providing space for continued discussions on missile-defense cooperation going forward."

Mr. Obama met for 90 minutes with Mr. Medvedev on the sidelines of a nuclear-security summit in Seoul. Their exchange about Mr. Obama's election came as they were seated in chairs and leaning in to speak privately to each other while shaking hands.

Mr. Obama is scheduled to have his first meeting with Mr. Putin in May when he hosts him at Camp David for the Group of Eight summit.

How is that NOT a deal?