Mr Duterte addressed concerns surrounding the resource-rich sea, most of which China claims as its own, at an economic forum in Tokyo, according to France24. However, the Philippines, Malaysia, Brunei, Taiwan and Vietnam also claim sovereignty over the waters. Mr Duterte said: “I love China… but it behooves upon us to ask, ‘is it right for a country to claim the whole ocean?”
Beijing and the 10-member Association of Southeast Asian Nations (ASEAN) have for years tried to create a code of conduct to govern the waters but so far to no avail.
Mr Duterte continued: “I am sad and bewildered – not angry, because I cannot do anything.
“I just hope China will come up with this ‘conduct’ soon.
He said the “longer it takes” the greater the chance the sea would be a “flashpoint of troubles”.
He added that France, Britain, and the United States are already “testing the waters”.
On Friday, Washington branded China’s militarisation of the territory as “excessive”.
Acting US Defence Secretary Patrick Shanahan said China’s installation of surface in the waters to air missiles was “overkill”.
He also called China’s actions over the disputed area “excessive” at a fence forum in Singapore.
The US and China have locked horns over the waters, which Beijing is dangerously territorial over.
China claims the huge stretch of water almost in its entirety and has been known to not take too kindly to foreign naval action in the area, especially by the US and allies such as Australia.
A number of other incidents involving lasers and the Chinese military have been reported as far away as Djibouti, where the warring US and China both have bases.
Last year, the US were left furious at China and alleged lasers had been aimed at aircraft that resulted in minor injuries to two of its pilots.
The claim surfaced again days ago, when it was alleged Australian pilots were targeted by the same devices.
China denies both claims.