The Philippines announced Friday it had officially informed the United States that joint patrols in the South China Sea patrols had been suspended, following orders from President Rodrigo Duterte.

"They have been suspended for the time being. They (Washington) know it already," Defence Secretary Delfin Lorenzana told reporters, adding he had relayed the decision to the commander of the US Pacific Command when he was in Hawaii at the start of this month.

Still, Lorenzana indicated he was still not 100 percent sure of Duterte's final plans.

"They will not be conducted anymore until we clarify if he (Duterte) means what he says," Lorenzana said.

The longtime allies began planning joint patrols under the previous Philippine government, which had sought to attract a greater US military presence in the region to counter Chinese efforts to take control of the South China Sea.

China claims nearly all of the sea, even waters close to 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.

Lorenzana said the United States and Philippines had conducted two "passing through" manoeuvres over the section of the sea claimed by Manila this year, but not actual "combat patrols".

Duterte, who began his six-year term on June 30, quickly shredded Aquino's strategy on China, seeking co-operation and dialogue with Beijing while diluting the Philippines' alliance with the United States.

He also repeatedly railed against the Philippines' former colonial ruler for criticising his war on crime, which has claimed more than 3,300 lives and raised concerns about extrajudicial killings.

"I have lost my respect for America," Duterte said on Tuesday, as he threatened to break ties completely with the United States.

Duterte had previously branded US President Barack Obama a "son of a whore".

He had also said he wanted US Special Forces out of the southern region of Mindanao, where they have been helping to quell Islamic militants, and threatened to scrap a 2014 agreement granting American troops increased access to Philippine bases.

Duterte also said he would cancel all 28 military exercises the two sides hold annually.

- Concrete actions -

However, until Friday, officials from both sides had said Duterte's pronouncements were not necessarily policy.

US officials had repeatedly said they had not been officially informed of Duterte's comments.

So the announcement that the joint patrols had been suspended was the first public confirmation that one of Duterte's anti-US comments had become policy.

Lorenzana said none of the other Duterte pronouncements had been officially delivered to the Americans.

But he did say the Philippines was planning to eject the US forces in the southern Philippines in the "near future", as he disclosed details of their normally secretive activities.

The US Special Forces began short-term deployments in 2002 to train Filipino troops in how to counter Islamic militants, with the American personnel peaking at about 600 before the operation was scaled down in 2014.

"There are actually very few of them (now), just about 157 people," Lorenzana said, adding they were stationed inside a large military camp on the outskirts of Zamboanga city on the main southern island of Mindanao.

"All they do is operate their drones and some intelligence equipment to help our troops in the south."

He said the drones flew over the militant strongholds of the Basilan and Sulu island groups, as well as central Mindanao where another small armed group had pledged alliance to the Islamic State group.

Lorenzana said those US forces would be asked to leave when the Philippines acquired its own drones.

"The president said that he doesn't want them to leave immediately but maybe in the near future," Lorenzana said.