Months of growing animosity between Beijing and Washington escalated again Monday, when China slapped sanctions on four U.S. officials, including three Republican members of Congress, and Secretary of State Mike Pompeo declared most of China’s maritime claims in the South China Sea “completely unlawful.”

“The world will not allow Beijing to treat the South China Sea as its maritime empire,” Pompeo said in a statement, accusing China of a “campaign of bullying” to control contested offshore resources other countries in the region also lay claim to.

“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. We stand with the international community in defense 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.”

Pompeo in effect upended previous U.S. policy that maritime disputes between China and other countries in the region should be resolved through U.N.-backed arbitration. His declaration places the United States on the side of China’s smaller neighbors – Brunei, Indonesia, Malaysia, the Philippines and Vietnam. All of them reject China’s claims of sovereignty in the waters around islands in the South China Sea.

Ever since a contentious meeting in Hawaii last month with China’s foreign policy chief, Yang Jiechi, Pompeo has repeatedly said the United States will watch Beijing’s actions to determine whether the ruling Chinese Communist Party wants to tone down the temperature on the heated rhetoric emanating both capitals. China and Iran have been forging new ties as the two countries have become the biggest targets of the Trump administration.

Pompeo’s remarks on the South China Sea came just hours after China announced sanctions on four U.S. officials, including prominent Republican senators Marco Rubio (Fla.) and Ted Cruz (Tex.), for “interfering in China’s internal affairs” through their condemnation of Beijing’s human rights abuses in the country’s Xinjiang region.

The other Americans targeted are Sam Brownback, the Trump administration’s ambassador for international religious freedom, and Rep. Christopher H. Smith, R-N.J.

No details were disclosed on what the sanctions would involve, but the move comes days after the Trump administration banned three Chinese officials from visiting the United States and froze any U.S. assets they might have.

The measures expand the tit-for-tat hostilities between Beijing and Washington – which already encompass trade, technology and media freedoms – into a new sphere.

“Xinjiang affairs are China’s internal affairs, and the U.S. has no right to interfere in them,” Foreign Ministry spokeswoman Hua Chunying told reporters in Beijing.

“We urge the United States to immediately withdraw its wrong decision,” she said, adding that China would make further decisions based on how the situation evolves.

China vowed to retaliate after the Trump administration used the Global Magnitsky Act to blacklist Chen Quanguo, the Communist Party secretary in the Xinjiang Uighur Autonomous Region in northwestern China and a member of the Politburo; Zhu Hailun, party secretary of the Xinjiang political and legal committee; and Wang Mingshan, party secretary of the Xinjiang public security bureau.

In addition to stopping them and their immediate family members from entering the United States, the designation freezes their U.S. assets and prohibits Americans from doing business with them.

The sanctions were part of a broader campaign against human rights abuses in Xinjiang, coming immediately after President Trump last week signed into law the new Uighur Human Rights Policy Act.

The law, which Rubio and Sen. Robert Menendez, D-N.J., introduced, was passed unanimously by the Senate and the House. It required the U.S. government to compile a report about the extent of the Chinese crackdown in Xinjiang and provide potential individual targets for sanctions under the Global Magnitsky Act.

More than a million people, most of them ethnic Uighurs, have been interned in huge detention camps across the northwestern region as part of a concerted effort by the officially atheist Communist Party to forcibly assimilate the mostly Muslim ethnic minorities into the majority Han culture.

The Communist Party says the measures are needed to “deradicalize” people, but the United Nations and many Western nations have condemned the campaign as a gross violation of human rights.

The Associated Press reported this month on draconian measures the Chinese government is taking to slash birthrates among Uighurs and other minorities, part of a drive to curb China’s Muslim population. These include forced contraception, sterilization and abortion.

In The Washington Post’s editorial section Monday, national security adviser Robert C. O’Brien said the United States would not stand by while the Communist Party committed these abuses.

“If the past century has shown us anything, it is that dangerous ideologies backed by powerful states rarely confine their malign conduct within their own borders,” he wrote. “The United States will thus continue to shine the light of truth on Xinjiang – for the Uighurs and for us all.”

Hua, the Foreign Ministry spokeswoman, said the U.S. sanctions were a “serious violation of basic norms governing international relations” and “severely undermine our bilateral relations.”

“The Chinese government is determined in safeguarding national sovereignty, security and development interests, and in fighting terrorists, violent separatists and religious extremist forces,” she said.

The mounting confrontation over Xinjiang comes amid a rapid deterioration this year in relations between the world’s two largest economies.

Trump and his senior officials have repeatedly accused China of covering up the outbreak of the novel coronavirus that began in the city of Wuhan at the end of last year and allowing it to spread across the world.

According to the government’s official tally, 4,634 people have died in China of COVID-19, the disease caused by the coronavirus. But in the United States, where Trump administration officials have been accused of being slow to act against the threat, the death toll has topped 132,000.

The State Department issued a travel warning for China over the weekend, telling U.S. citizens to exercise increased caution “due to arbitrary enforcement of local laws for purposes other than maintaining law and order,” which may include detention, prolonged interrogations and exit bans.

Hua said the travel alert was misguided. “People in the U.S. are worried about a return of notorious McCarthyism, so by issuing this travel alert under such circumstances, the U.S. is apparently seeking pretexts for arbitrarily undermining Chinese citizens’ rights and interests in the U.S.,” she said.

Comments are not available on this story.