President Ferdinand "Bongbong" Marcos Jr. on Thursday said the Chinese government's refusal to recognize the Philippines' rights over the West Philippine Sea has been hindering negotiations on possible joint oil and gas exploration projects in the busy waterway.

In a media interview on the sidelines of an event at Quezon City Hall, Marcos Jr. said Manila has had oil exploration partners in the past, but "constitutional problems" have impeded deals to exploit energy reserves inside the country's 200-mile exclusive economic zone.

"We actually had many partners before. The problem was the negotiations stopped. If you can remember, then-Foreign Affairs Secretary Teddy Boy Locsin made a pronouncement saying that negotiations have been discontinued because of constitutional problems," Marcos said in Filipino.

"What really happened there is… China is claiming it as theirs when it is actually ours," he stressed.

The Chief Executive emphasized that the Philippine government must "fight" for its rights over the contested waters.

"For China, it is just a small thing, but for us, it is a big thing. So, we really need to fight for it and take advantage if oil can be really found there," he said.

In June this year, Locsin announced that the Duterte administration had decided to end talks over joint energy exploration with China due to a potential "constitutional crisis."