Vietnam and China agreed Monday to avoid conflicts in the hotly contested South China Sea, as a new pathway to dialogue on easing tensions was opened with other Southeast Asian nations, SCMP reported.

The communist neighbours have long sparred over the sea, through which $5 trillion in shipping trade passes annually and which is believed to sit atop vast gas reserves.

Hanoi and Beijing agreed Monday to keep the peace in the sea, the countries said in a joint statement during a state visit to Hanoi by Chinese President Xi Jinping.

They agreed to “well manage disputes at sea, make no moves that may complicate or expand disputes, (and) maintain peace and stability on the East Sea,” the Vietnamese version of the statement said, using Hanoi’s term for the waters.

China claims nearly all of the sea, even approaching the coasts of its neighbours. It is also partly claimed by the Philippines, Malaysia, Brunei and Taiwan in addition to Vietnam.

China has in recent years built artificial islands and airstrips capable of hosting military installations in contested areas to cement its claims, inflaming tensions with its neighbours.

On Sunday US President Donald Trump offered to help Vietnam resolve the long-simmering tensions.

“If I can help mediate or arbitrate, please let me know... I am a very good mediator,” Trump said on his own state visit to Hanoi at the tail end of his marathon tour of Asia.

Vietnam offered no response.