MANILA (DPA) - Philippine President Rodrigo Duterte jokingly suggested that the United States should enforce its mutual defence treaty with the country and start a war with China.

"I'm calling now, America," he said in a television show hosted by a Christian pastor who is a staunch supporter and friend.

"I am invoking the Philippine-US pact, and I would like America to gather all their Seventh Fleet in front of China," he said on the show that aired late on Tuesday (July 16) as the two discussed the long-standing territorial dispute over the South China Sea.

Mr Duterte said he would even ask the US to allow him to "press" the button that would start the war, which he said may result in the "end" of the western province of Palawan, which is nearest the disputed territories.

"We can just wait for just like a big hole coming our way to suck us to eternity," he quipped.

On Wednesday, presidential spokesman Salvador Panelo said Mr Duterte takes the South China Sea dispute seriously but suggested that these particular comments were made in jest.

Mr Panelo said Mr Duterte was being sarcastic because he was exasperated by critics who have called on the president to invoke the 68-year-old mutual defence pact in order to stop China's activities in the sea.

"He is annoyed that he is being used as bait," Mr Panelo said. "So he challenged his critics."

US authorities have said that Washington would uphold its obligations under the 1951 Mutual Defence Treaty, which binds both countries to aid each other in the event of foreign aggression.