MANILA, Philippines -- Philippine President Rodrigo Duterte said Tuesday he will not abrogate a defence treaty with the United States but questioned its importance and that of joint combat exercises, which he says only benefit America.

Duterte pressed his criticism of the United States and his country's engagement with the American military in a speech as U.S. Marines and their Philippine counterparts ended combat drills a day early in a separate ceremony. A U.S. general, in contrast, underscored the need for the joint drills to brace for potential crises.

Duterte, who labels himself a socialist, has had an uneasy relationship with the U.S. and a falling out with President Barack Obama, whom he has lambasted for criticizing his deadly anti-drug fight. Despite his constant anti-U.S. pronouncements, Duterte said he would not abrogate the mutual defence treaty with the U.S. but questioned the need for it.

"I do not mean to cancel or abrogate the military alliances," Duterte said in a speech before new government officials at the presidential palace. "But let me ask you ... do you really think we need it?"

He did not clearly specify his reason for questioning the treaty alliance but said if a conflict pitting the world's most powerful nations breaks out, "there will be no more American aid to talk of." He added that when Russia annexed Crimea, "America wasn't able to do anything."

Duterte has announced he will end the joint combat exercises, which China has opposed. His defence secretary, Delfin Lorenzana, said he has asked Duterte for a reconsideration, and has explained to the president the importance of the approximately 28 annual joint military exercises, including three major ones that involve thousands of troops, in preparing for natural disasters and other contingencies. U.S. military officials want to continue the joint manoeuvrs, Lorenzana said Friday.

Duterte, however, has remained criticial, saying Tuesday that U.S. troops take back with them the high-tech and powerful weapons after each drill. "So what's the point?" he asked. "They're the ones who benefited, they're the ones who learned but we got nothing."

In Washington, the top U.S. diplomat for East Asia said Tuesday the U.S. will honour its commitments to the Philippines and expects its Southeast Asian ally to do the same.

Assistant Secretary of State Daniel Russel said the U.S. values the relationship and wants to keep it on an "even keel."

"We're prepared, as we always have been, to honour our commitments and the obligations that we have to the Philippines and we expect the same in return," Russel said at an event held by the Center for Strategic and International Studies think-tank .

Russel said the U.S. has no problem with the Philippines discussing its territorial and maritime disputes with China if it is done on terms acceptable to the Philippines and consistent with international law.

That was an apparent reference to a July ruling by an international tribunal in a case brought by the previous Philippine government that found that China's sweeping claims to most the South China Sea on historical grounds were invalid under a U.N. treaty.

The joint drills that ended Tuesday in an austere ceremony were held in an air of uncertainty because of Duterte's warning that they would be the last under his rule.

U.S. Marine Brig. Gen. John Jansen said the drills underscored the depth of the U.S.-Philippine alliance "and the commitment to be there when it counts," adding both countries benefited from the exercises.

"It makes us all better," Jansen said. ""It not only makes us better but more capable and effective as an integrated force that provides a capability that we might apply to our treaty obligations in the future, whether it be in humanitarian assistance and disaster relief operations, assistance in internal security, or in other types of crisis."

A Philippine military spokesman for the exercises, Col. Ariel Caculitan, said the manoeuvrs ended a day early because of adjustments resulting from stormy weather forecasts, among other reasons, and had no connection with Duterte's criticism of the drills.