Philippine President Rodrigo Duterte said on Friday he was not sure why China's commerce minister had cancelled a trip to his country, and that Beijing misunderstood his foreign minister's comments about its militarisation in the South China Sea.

In a speech in which he expressed his intention to have solid ties with China, Duterte said there was no need to press it to abide by an international arbitration ruling last year.

Foreign Secretary Perfecto Yasay, as chair of a meeting of Southeast Asian leaders, said on Tuesday said the region had "grave concerns" about Chinese weapons installations on manmade islands in the South China Sea.

"I would like to assure China, and this is what I had committed to do when I was there, that we will talk as friends," he said, referring to a trip he made to China last year.

He also said his country, despite its longstanding alliance with the United States, was "not duty-bound to follow" its foreign policy. (Reporting by Martin Petty and Neil Jerome Morales; Editing by Robert Birsel)