Philippine President Rodrigo Duterte vowed Sunday he will not "barter" away territory and economic rights ahead of a visit to Beijing, where he hopes to mend ties frayed by a row over the South China Sea.

Duterte will head to Beijing on Tuesday -- after a state visit to Brunei that kicks off late Sunday -- and will be bringing along a large business delegation in a bid to secure Chinese investment as relations sour between Manila and its traditional ally the United States.

Duterte Sunday said he would also raise with Chinese President Xi Jinping a ruling by an international tribunal that outlawed Beijing's claim to most of the South China Sea, including waters close to the Philippine coast.

China, which rejected the ruling, claims nearly all of the strategically vital waters and has in recent years built artificial islands in the disputed areas that are capable of hosting military bases.

Duterte had earlier vowed not to "taunt or flaunt" the July ruling as he aims to improve trade and investment ties, which some critics warned could entail surrendering exclusive economic rights to the sea to Manila's powerful neighbour.

"I will be very careful not to bargain anything (away) for after all I cannot give what is not mine and which I am not empowered to do by any stretch of imagination," he told reporters in Davao city.

"The international tribunal's decision will be taken up, but there will be no hard impositions. We will talk and we will maybe paraphrase everything in the judgment and set the limits of our territories and (exclusive) economic zones."

During the election campaign, Duterte said he was willing to "set aside" the sea dispute in return for China building a railway through the impoverished southern Philippine region of Mindanao.

His willingness to launch negotiations with China over the dispute has been welcomed by Beijing.

On Sunday Duterte said he agreed with senior Supreme Court justice Antonio Carpio that the president could be impeached and removed from office if he gave away Scarborough Shoal, a fishing ground within the Philippines' exclusive economic zone that China seized in 2012.

"He is correct. I would be impeached. It's an impeachable offence. I don't fight with that statement. It's all correct it's all legal and so I agree with him," Duterte said.

"It belongs to the Filipino people. I cannot be the sole authorised agent, for that is not allowed under the constitution."

Since coming to power in May, Duterte's push to restore ties with China has been accompanied by fiery rhetoric against the United States.

He scrapped a series of annual war games and joint South China Sea patrols with the US military after President Barack Obama criticised Manila's brutal war on drug crime which has left more than 3,000 people dead.