The U.S. and Russia agreed to a prisoner swap involving Marc Fogel, an American schoolteacher who the Biden administration had deemed wrongfully detained by Russia, in a diplomatic move that the White House said could move forward negotiations to end the war in Ukraine.

One advocacy group says more than 30 American hostages and wrongful detainees are being held in other countries.

"I feel like the luckiest man on Earth right now," Marc Fogel said, standing alongside President Trump in the White House upon his return.