President Donald Trump told Spain's leader Mariano Rajoy on Tuesday that the United States is committed to NATO, the White House said, despite his past criticism of the transatlantic military alliance.

Trump's first conversation with Rajoy since taking office on January 20 served to "reaffirm the strong bilateral partnership across a range of mutual interests," the White House said.

"President Trump reiterated the US commitment to the North Atlantic Treaty Organization (NATO) and emphasized the importance of all NATO allies sharing the burden of defense spending."

The American president is due to meet with fellow NATO leaders in May. The United States provides significant funding to NATO, and Trump has previously urged other member nations to step up their contributions.

European leaders are concerned about Trump's virulent criticism of NATO -- he has dubbed the transatlantic military alliance "obsolete" -- at a time when it stands as the main defense against Russia's President Vladimir Putin.

Trump's friendly stance toward Putin has been under scrutiny, and triggered consternation among European allies, since he won the US election in November.

Trump took office with US-Russian ties at new lows amid accusations by American intelligence agencies that the Kremlin hacked Democratic Party emails as part of a pro-Trump campaign to influence the election.

Trump and Rajoy also discussed "shared priorities, including efforts to eliminate ISIS," the White House said, referring to the Islamic State group.

"The leaders agreed to continue close security, economic and counterterrorism cooperation."