The firebrand Duterte pledged to honor a longstanding security treaty with the United States but said China opposed joint marine drills in the Philippines starting next week and there would be no more war games with Washington after that.

"I am serving notice now to the Americans, this will be the last military exercise," Duterte said during a visit to Vietnam. "Jointly, Philippines-U.S.: the last one."

Duterte's remarks gave one of the strongest signs yet of fissures in a historic alliance that Washington has relied upon as it tries to cement its influence in Asia to counterbalance China's rapid rise. His foreign minister later said his comments had been taken out of context.

The Philippine military and U.S. Marines are due to hold annual amphibious landing exercises from Oct. 4 to 12 in the north of the Philippines main island Luzon. Military leaders from the two countries have also started preparing for a new set of exercises next year.