A top Chinese diplomat is visiting Vietnam amid a looming ruling by an international court on the South China Sea.

State Councilor Yang Jiechi's visit comes as the Permanent Court of Arbitration in the Hague is expected to issue a ruling soon on a case filed by the Philippines contesting Beijing's claims to most of the South China Sea.

Beijing says that more than 40 countries support its position, a claim doubted by experts.

Tran Cong Truc, former head of government's border committee, said Yang may try to lobby Vietnamese leadership on the issue but that Vietnam's stance on opposing Chinese claims will not change.

Vietnamese Foreign Minister told Yang that bilateral relations will continue a positive trend despite challenges such as the disputes seas.