President Barack Obama thanked Singapore for its military help Tuesday, as the first of a new generation of US coastal warships steamed to the city state to support his policy "pivot" to Asia.

Obama made a point of pouring praise on Singapore as an example to the world and as an important ally and source of counsel for Washington in Asia as he welcomed Prime Minister Lee Hsien Loong for Oval Office talks.

The meeting took place just before the USS Freedom, a littoral combat ship, arrives to start a temporary deployment, one of four of the stealthy vessels that will be rotated through Singapore.

"We have extremely close military cooperation," Obama said ahead of the meeting, as he praised Singapore as "one of the most successful countries in the world."

"I want to thank Singapore for all the facilities that they provide that allow us to maintain our effective Pacific presence."

Lee said that Singapore was "very happy" that the United States under Obama had been placing greater emphasis on its relations with the dynamic Asia-Pacific region, in a policy approach the White House calls "rebalancing."

"We look forward particularly in the next few weeks to welcoming the first littoral combat ship, which will be arriving in Singapore and we will be playing host to it for a few months," Lee said.

Singapore plans to host up to four of the stealthy vessels, which are designed to operate in shallow coastal waters and are designed to project US power in the fight against terrorists and pirates.

Singapore has traditionally been a key source of advice and interpretation of events in Asia, particularly in China, for US administrations, and Obama said that Lee had been especially helpful to him.

"Personally, there are very few world leaders who I am more appreciative of in terms of their advice, counsel and thoughtful analysis than Prime Minister Lee," Obama said.

Lee described US-China ties as perhaps the most important diplomatic relationship in the world, and said he was happy that Washington, which has sent top officials to Beijing in recent weeks, was focusing on the issue.

"Singapore will do our part to do what we can to help America engage the region constructively, productively, and in a way in which it fosters stability and prosperity for all the countries," he said.

The meeting focused on regional security challenges as well as trade, with Singapore and the United States key players in the evolving Trans-Pacific Partnership (TPP) pact.

The Obama administration's shift of military and diplomatic resources to the Asia-Pacific is currently being challenged by a new outburst of belligerence by North Korea.

The president elected not to answer shouted questions from reporters about the issue in his photo-op with Lee.

Earlier, White House press spokesman Jay Carney said that Washington would like China and Russia to do more to restrain Pyongyang.

"It's not a mystery to anyone that China has ... influence on North Korea or potentially has influence on North Korea.

"We have in the past -- and we are now -- urged China to use that influence to try to affect North Korean behavior.

"That is also true of our interactions with the Russians."