Philippine President Rodrigo Duterte is willing to hold military exercises with China but not longtime ally the United States, Chinese media quoted him Monday as saying on the eve of a state visit.

Duterte heads to Beijing on Tuesday for a four-day trip that appears set to cement his dramatic foreign policy tilt away from United States, which he has railed against for criticising his deadly war on crime.

"It's only China (that) can help us," China's state-run Xinhua news agency quoted Duterte as saying in an interview ahead of his visit.

Duterte also told Hong Kong-based Phoenix Television he was willing to hold joint military exercises with China and Russia.

"Yes, I will. I have given enough time for the Americans to play with the Filipino soldiers," Duterte said when asked if he was open to war games with those two nations, as he reiterated he would no longer hold any more with the United States.

"This will be the last. It has been programmed. I do not want my soldiers to be humiliated," Duterte said, in reference to one set of war games in the Philippines that ended last week.

Duterte has sought to reshape his nation's foreign relations since taking office on June 30 by pivoting towards China and Russia while moving away from the United States, the Philippines' former colonial ruler and mutual defence ally.

Duterte has repeatedly expressed anger over American criticism of his war on crime, which has claimed more than 3,700 lives and raised fears of mass extrajudicial killings.

He has branded US President Barack Obama a "son of a whore" and told him to "go to hell".

But, signalling his shift to China is also for pragmatic reasons, Duterte has repeatedly ridiculed the United States for what he sees as its weakening economic and military influence around the world.

In the Xinhua interview Duterte again thanked China for not criticising the crime crackdown as he held out the Philippines' hand for soft loans and other forms of financial help.

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- 'China never criticises' -

"China never criticises. They help us quietly," Duterte said, according to Xinhua.

Duterte is bringing an entourage of hundreds of businessmen with him to Beijing, and Philippine media have said deals worth billions of dollars are expected to be announced during the trip.

Asked if he would seek to buy military equipment from China during his visit, Duterte told Phoenix Television: "Yes, but not really in (large) numbers."

Duterte said he would also need small, fast attack boats from China to fight "terrorism".

"If China does not help us in this endeavour, we will have a hard time fighting terrorism," he said without elaborating, according to Phoenix Television.

Bilateral relations worsened under Duterte's predecessor, Benigno Aquino, who tried to challenge China's expansionism in the South China Sea.

China claims nearly all of the strategically vital sea, even waters approaching the Philippines and other Southeast Asian nations, and has in recent years built artificial islands in the disputed areas that are capable of hosting military bases.

To counter China, Aquino allowed a much greater American military presence in the Philippines and started joint patrols in the sea with US forces.

He also filed a legal case at a UN-backed tribunal, which ruled in July that China's claims to most of the sea had no legal basis. Beijing refused to accept the ruling.

Duterte has said he does not want to use the verdict to pressure China. In recent weeks he has also cancelled the joint sea patrols with the United States and said he may cancel a pact that allows a greater US military presence in the Philippines.