Three Korean-Americans who were detained in North Korea for more than a year were greeted by President Donald Trump beneath a giant American flag after they returned to the mainland U.S. early Thursday.

Despite a middle-of-the-night landing, first lady Melania Trump, Vice President Mike Pence and a host of senior administration officials joined Trump to celebrate the occasion.

The men, Kim Dong Chul, Kim Hak Song and Tony Kim, had been released Wednesday amid a warming of relations between the longtime adversaries.

Trump called it a "great honour" to welcome the detainees to the U.S. and added, "The true honor is going to be if we have a victory in getting rid of nuclear weapons."

Joined by the former detainees, Trump thanked North Korea's Kim Jong Un for releasing the Americans, and said he believes Kim wants to reach an agreement on denuclearizing the Korean peninsula.

"I really think he wants to do something," the president said.

The men, Kim Dong Chul, Kim Hak Song and Tony Kim, had been released Wednesday amid a warming of relations between the longtime adversaries.