WASHINGTON - The White House confirmed on Tuesday that President Donald Trump will join fellow NATO leaders for a key May summit in Brussels, as the US administration seeks to quash questions about Trump's support for the alliance.

The Trump administration has been scrambling to reaffirm its commitment to Washington's military alliances - including NATO - after the Republican billionaire called into question their usefulness during the presidential race.

News that Secretary of State Rex Tillerson would skip a NATO meeting in April - but travel to Russia the same month - did little to allay concerns.