KUALA LUMPUR - President Obama today endorsed the Malaysian government's handling of the disappearance of Malaysia Airlines flight MH370, giving an important boost to Prime Minister Najib Razak amid swirling public criticism and private grumblings among some U.S. officials that his administration has bungled the effort.

"I can't speak for all the countries in the region, but I can say the U.S. and other partners have found the Malaysian government eager for assistance, have been fully forthcoming with us in terms of the information they have, and this is a joint effort," Obama said at a news conference.

The president said the Malaysians have been working "tirelessly" to recover the missing Boeing 777 and determine what brought it down, even though no wreckage or remains have been found.

"It's not easy," Obama said. "If in fact the plane went down in the ocean in this part of the world, that is a big, big place. And it is a very challenging effort, and very laborious effort that's going to take some time."

He offered condolences to families of the victims and said their pleas for transparency in the investigation were understandable and legitimate.

"I want to again express the deepest condolences of the American people to all the families who lost loved ones on that flight - Malaysian, American, Chinese - and people from many other nations," he said.

Obama said during his meeting with Najib that both men discussed "some of the lessons that are being learned from this tragedy" and how the U.S. and Malaysia can improve cooperation in the future.