President Rodrigo Duterte is planning separate visits to China and Japan next month, his first foreign trips outside Southeast Asia since assuming leadership on June 30, diplomatic sources said Thursday.

The trip to China, which sources say is scheduled for the third week of October, will show whether Duterte will stay true to his pronouncements that he will assert Manila's victory in an international arbitration case against Beijing over disputed territories in the South China Sea.

"I am willing to talk. I am going to China. And if it is just the two of us there, I will present the problem to him. And I would say to him, 'this piece of paper, the arbitral award, we don't go out of the four corners of this paper. Let's talk,' " Duterte, apparently referring to Chinese counterpart Xi Jinping, said in a speech Thursday, without fully confirming the plan.