WASHINGTON — The release of three American prisoners cleared away a last obstacle on Wednesday to a landmark nuclear summit meeting between President Trump and North Korea’s leader, Kim Jong-un.

North Korea freed the prisoners, all Americans of Korean descent, even as the two countries finalized details for a meeting between their leaders. The move was North Korea’s most tangible gesture aimed at improving relations with the United States since Mr. Trump took office.

The resolution of the prisoner standoff hardly guaranteed success at the meeting, which will grapple with the far more complicated issues of North Korea’s nuclear arsenal, divisions on the peninsula and security in Asia. But American officials said it sent another signal that North Korea may be serious about ending its long confrontation with the United States and its allies after nearly seven decades of mutual antagonism.

Mr. Trump exulted over the release and publicly entertained talk that he could even win a Nobel Peace Prize for his diplomacy. He was so eager to associate himself with the freed prisoners that he decided to personally travel to Joint Base Andrews outside Washington in the middle of the night to welcome them back to the United States, something other presidents have not typically done in similar circumstances.