President Barack Obama has defended the Malaysian government's handling of its fruitless search for Malaysia Airlines Flight 370, saying officials are working tirelessly to find the aircraft that is believed to be at the bottom of the Indian Ocean.

Commenting after meetings with Malaysian prime minister Najib Razak, Mr Obama said he knows how hard officials are working because of his consultations with his own team and because of all the US assets involved in the massive search effort.

"The Malaysian government is working tirelessly to recover the aircraft and investigate exactly what happened," Mr Obama said at a news conference, with the prime minister at his side.

"I can't speak for all the countries in the region but I can say that the United States and other partners have found the Malaysian government eager for assistance and fully forthcoming with us in terms of the information that they have."

The Boeing 777 carrying 239 people, most of them Chinese, vanished nearly two months ago. Anguished relatives of the passengers are unhappy with the search effort. Many of them have protested outside the Malaysian Embassy in Beijing in the past week.

Mr Obama said he understands the heartache and suffering loved ones of the passengers are feeling, but he said it will take even more time to find the plane because of the huge amount of ocean that is being scoured in the search operation.

"Obviously, we don't know all the details of what happened but we do know that, if in fact the plane went down in the ocean in this part of the world, that is a big place and it is a very challenging effort and laborious effort that's going to take quite some time."

Mr Obama arrived yesterday in Malaysia as part of a week-long tour of Asia, following stops in Japan and South Korea. He heads to the Philippines tomorrow.