WASHINGTON – President Barack Obama says NATO continues to be the cornerstone of collective defense for the U.S. and Europe.

Obama is hosting NATO Secretary General Jens Stoltenberg at the White House for an Oval Office meeting. He says they discussed the fight against the Islamic State group as well as potential operations in Libya.

Obama is also calling attention to the migrant crisis stemming from Syria’s civil war. He says the migrants are taking very dangerous trips and that the response must be “humane and thoughtful.”

Obama says the leaders also conferred on Afghanistan, Ukraine and resolving conflicts with Russia.

Their meeting comes as Republican presidential candidate Donald Trump has been questioning NATO’s relevance. Stoltenberg says NATO remains “as important as ever.”