President Obama was interrupted by a heckler who questioned his foreign policy toward Russia and Ukraine during an address to a Democratic National Committee meeting in Washington.

“Tell the public your plan -- tell us about your plan for nuclear war with Russia,” an audience member shouted, according to reports.

Obama paused his speech, responding, “Who’s that back there?” to laughter.

“What the heck are you talking about?” Obama added, as the audience applauded and cheered the president.

“I don't know anything about that plan,” he continued. “I don't know what you've been reading. Let me return to what I was talking about,” he continued.

Obama also joked that the heckler “thought happy hour started earlier.”

Obama earlier on Friday afternoon addressed the turmoil in Ukraine after Kiev accused Russia of an “armed invasion,” with reports that Russian troops had taken over airports in Crimea.

Obama warned Russia in a statement from the White House that “there will be costs” for any military intervention in Ukraine.

The president said he was “deeply concerned” by reports of Russian troop movements and urged Moscow to stand down and work with the international community to bring stability to Ukraine.