MANILA - President-elect Rodrigo Duterte says he has told US President Barack Obama the Philippines will remain allied with the US in a spat with China over the South China Sea, but may negotiate with Beijing directly if multilateral talks falter.

In a TV interview late on Tuesday (May 17), Mr Duterte said he assured Mr Obama during a phone conversation that "we will continue with our mutual interests, and that we are allied with the Western (world) on this issue on (the South) China Sea".

"But I gave him an inkling that, well, I would agree to just go with you. But if it goes on still waters… there's no wind to move the sail, I might opt to go bilateral," he told a news programme on GMA-News.

He said Mr Obama advised him to wait for a ruling, due in weeks, from a United Nations arbitration court on a case the Philippines filed challenging China's claims to nearly all of the South China Sea.

China claims nearly all of the South China Sea, through which US$5 trillion (S$6.86 trillion) worth of ship-borne trade passes each year. The Philippines, Vietnam, Malaysia, Brunei and Taiwan also have competing claims to parts of the waterway.

Mr Duterte, who will be sworn into office on June 30, earlier said he intends to continue backing multilateral efforts - including Asean's own initiatives - to settle disputes with China.

But he also repeated a campaign pledge to hold direct talks with China, if other negotiations falter in two years.

He has suggested he is willing to set aside Manila's claims if China agrees to build railways across the Philippines and join in exploring for resources in contested waters.

Mr Duterte said he wants more friendly relations between the Philippine and China.

"I would rather be friendly with everybody," he said.