Hanoi has called for an international tribunal in The Hague to deliver a "fair and objective" ruling in an arbitration case lodged by the Philippines that challenges China's expansive claims in the East Vietnam Sea.

In a carefully worded statement two days after the court announced July 12 as the verdict date, Vietnam's foreign ministry said it hoped the ruling would provide a basis for peacefully resolving rows.

Vietnam is not a direct party to the case but stands to gain if the verdict favors Manila. Like the Philippines, it is also at odds with China, although it is wary not to push too far against a major trade partner.

"Vietnam has always been observing the development of the case and wants the arbitration court to deliver a fair and objective decision, creating a basis to peacefully resolve disputes in the East Vietnam Sea," the Vietnamese foreign ministry spokesman, Le Hai Binh, said in a statement late on Friday.

Though the wording was similar to those used by numerous countries, Vietnam's statement stopped short of calling for the ruling to be respected.

China has gone to great efforts to show the Permanent Court of Arbitration has no jurisdiction on the case, and Beijing will therefore not recognize it. China's official Xinhua news agency called it a "law-abusing tribunal".

The case seeks an interpretation of the United Nations Convention on the Law of the Sea (UNCLOS), to which Beijing is a signatory.

The East Vietnam Sea is one of the world's most vital shipping lanes, with about $5 trillion of goods passing annually through waters contested in parts by six countries, several of which are undergoing military buildups.