"As Beijing has failed to put forth a lawful, coherent maritime claim in the South China Sea, the United States rejects any PRC (People’s Republic of China) claim to waters beyond a 12-nautical mile territorial sea derived from islands it claims in the Spratly Islands," U.S. Secretary of State Mike Pompeo said in a press statement on Monday.

"As such, the United States rejects any PRC maritime claim in the waters surrounding Vanguard Bank (off Vietnam), Luconia Shoals (off Malaysia), waters in Brunei’s EEZ, and Natuna Besar (off Indonesia)."

Any PRC action to harass other states' fishing or hydrocarbon development in these waters, or to carry out such activities unilaterally, is unlawful, it warned.

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, it said.

"Beijing uses intimidation to undermine the sovereign rights of Southeast Asian coastal states in the South China Sea, bully them out of offshore resources, assert unilateral dominion, and replace international law with ‘might makes right’."

In this context, it recalled Yang Jiechi, the former Chinese foreign minister, telling his ASEAN counterparts in 2010 that "China is a big country and other countries are small countries and that is just a fact."

Pompeo's statement explicitly sides with Southeast Asian nations including the Philippines and Vietnam, after years of the U.S. saying it took no position on individual claims.

He said: "America stands with our Southeast Asian allies and partners in protecting their sovereign rights to offshore resources, consistent with their rights and obligations under international law."

The Chinese embassy in the U.S. responded on Tuesday saying the U.S.’ statement "disregards the efforts of China and ASEAN countries for peace and stability in the South China Sea, deliberately distorts the facts and international law including the United Nations Convention on the Law of the Sea (UNCLOS), exaggerates the situation in the region, and attempts to sow discord between China and other littoral countries.

"The accusation is completely unjustified. The Chinese side is firmly opposed to it."

Earlier this month the U.S. had also criticized China’s military exercises near Vietnam's Paracel Islands, calling it a violation of China's commitments to maintain stability in the region.

"Conducting military exercises over disputed territory in the South China Sea is counterproductive to efforts at easing tensions and maintaining stability," the U.S. Defense Department had said, adding that the exercises went against China's commitments under the 2002 Declaration on the Conduct of Parties in the South China Sea to avoid actions that would complicate or escalate disputes and affect peace and stability.

Vietnam calls the South China Sea the East Sea.

China has taken a series of provocative actions in the waters since the start of this year as countries around the world were focused on battling the Covid-19 pandemic.

It formed the so-called ‘Xisha’ and ‘Nansha’ districts in Vietnam’s Hoang Sa (Paracel) and Truong Sa (Spratly) Islands, sank Vietnamese fishing vessels off the Paracels, unilaterally issued a fishing ban and sent a ship to harass a Malaysian oil and gas exploration vessel.

It recently announced a vegetable farming project on Woody (Phu Lam) Island in the Paracels to strengthen its illegal sovereignty claim, and sent two diplomatic notes to the U.N. to make the infamous Four Sha claim, which covers a broader swath of territory than the notorious, illegal nine-dash line.

Vietnam has repeatedly protested China’s provocative, illegal actions and urged it to desist.