WASHINGTON - The United States formally rejected most of China's claims to the South China Sea on Monday (July 13), issuing a statement that backed an international arbitral tribunal's ruling in 2016 that they are illegal.

"Beijing's claims to offshore resources across most of the South China Sea are completely unlawful, as is its campaign of bullying to control them," said Secretary of State Mike Pompeo.

China responded almost immediately with the embassy here saying it firmly opposed the statement. An embassy spokesman said the US had deliberately distorted the facts and international law, exaggerated the situation in the region, and attempted to sow discord between China and other coastal states in the South China Sea.

"The US is not a country directly involved in the disputes. However, it has kept interfering in the issue," said the spokesman in a statement.

"We advise the US side to earnestly honour its commitment of not taking sides on the issue of territorial sovereignty, respect regional countries' efforts for a peaceful and stable South China Sea and stop its attempts to disrupt and sabotage regional peace and stability," the spokesman added.

In his statement, Mr Pompeo said the US was aligning its position with the tribunal's decision in 2016, which rejected China's maritime claims as having no basis in international law.

China claims a large swathe of the South China Sea within its "nine dash line", including waters and maritime entitlements within the exclusive economic zones of other coastal states like Malaysia, Indonesia, Vietnam and the Philippines.

Those claims were rejected in 2016, almost exactly four years ago, by an international arbitral tribunal constituted under the United Nations Convention on the Law of the Sea (Unclos), in a case brought by the Philippines.

While Washington has objected to China's claims before, sending navy ships to the contested waters for freedom of navigation operations, analysts said that Monday's statement is the first time the US has definitively rejected the claims.

"The statements themselves represent an evolution, rather than a sharp break from, prior US policy towards the South China Sea. It makes certain positions which the US has implicitly held for many years more open and explicit," said Mr Patrick Chovanec, an adjunct professor at Columbia University's School of International and Public Affairs, on Twitter.

He added: "It potentially lays the legal foundation for the US to take more assertive action contesting China's efforts to control, and interfere with other countries activities, in the South China Sea...if it wishes and is prepared to do so."

In the statement, Mr Pompeo explicitly sided with South-east Asian nations, saying: "The world will not allow Beijing to treat the South China Sea as its maritime empire.

"America stands with our South-east Asian allies and partners in protecting their sovereign rights to offshore resources, consistent with their rights and obligations under international law.

"We stand with the international community in defence of freedom of the seas and respect for sovereignty and reject any push to impose "might makes right" in the South China Sea or the wider region," he added.

Chinese foreign ministry spokesman Zhao Lijian said at a media briefing yesterday that China "never seeks to establish a maritime empire in the South China Sea".

He added that it "always treats the neighbouring countries of the South China Sea as equals, and always maintains the utmost restraint in safeguarding the sovereignty and rights of the South China Sea".

Mr Zhao added that China was committed to working together with Asean countries to maintain peace and stability in the South China Sea, and that they were intensively negotiating a more binding Code of Conduct in the waterway to jointly safeguard peace and stability and freedom of navigation.

US Assistant Secretary of State for East Asian and Pacific Affairs David Stilwell said there were "clear red flags" about Beijing's intentions in talks over the Code of Conduct, however.

Speaking at a webinar organised by the Center for Strategic and International Studies on Tuesday, Mr Stilwell said that behind closed doors, Beijing had pushed Asean states to accept limits on core matters of national interests, including who they can partner with for military exercises and offshore drilling, and dilute their references to international law.

"These are demands of a bully, not a friendly neighbour. Beijing may have backed off its arbitrary 2021 deadline for concluding the talks, but its hegemonic goals remain," he said on Tuesday.

Washington and Beijing also tussled over Beijing's embrace of international law. Mr Stilwell said that Beijing liked to present itself as a champion of multilateralism but had dismissed the ruling of the international tribunal as a piece of paper.

Mr Zhao criticised the US for citing Unclos, pointing out that Washington has refused to ratify that international convention.