On Tuesday, China slammed the United States’ deployment of an aircraft carrier to conduct “routine operations” in the South China Sea, calling it a pretense to undermine its sovereignty.

“China always respects the freedom of navigation and overflight all littoral countries enjoy under international law,” Chinese Foreign Ministry spokesman Geng Shuang said at a daily news briefing, according to Reuters.

“But we are consistently opposed to relevant countries threatening and damaging the sovereignty and security of littoral countries under the flag of freedom of navigation and overflight,” Geng said. “We hope relevant countries can do more to safeguard regional peace and stability.”

China has built multiple islands in the sea and claims almost all its resource-rich waters — although Brunei, Malaysia, the Philippines, Taiwan, and Vietnam all claim parts of it — and about $5 trillion worth of trade passes through the sea each year.

The U.S. has criticized China’s construction of the islands, as well as a build-up of military facilities on the islands. The U.S. Navy sent the USS Carl Vinson, along with its strike group, through the South China Sea on Saturday, to conduct “routine operations.”

Prior to arriving in the South China Sea, the strike group conducted training off the islands of Hawaii and Guam, the Navy said.

“The training completed over the past few weeks has really brought the team together and improved our effectiveness and readiness as a strike group,” said Rear Adm. James Kilby, commander of the strike group.

“We are looking forward to demonstrating those capabilities while building upon existing strong relationships with our allies, partners, and friends in the Indo-Asia-Pacific region,” he said.

The last time the Vinson deployed to the South China Sea was in 2015, to conduct a bilateral exercise with the Royal Malaysian Navy and Royal Malaysian Air Force, the Navy said in a statement.

The Vinson first operated in the South China Sea in 1983 and has operated there during 16 previous deployments over its 35-year history, it added.

Other U.S. ships have navigated the South China Sea last year, to counter China’s claims of sovereignty, but this deployment was the first under President Trump.

The Vinson’s deployment to the area comes about two weeks after a Chinese aircraft that patrols the skies and detects threats flew within 1,000 feet of a U.S. surveillance aircraft. Pentagon officials had played that event down as unintentional.

It also comes after a Navy plan was sent up to Defense Secretary Jim Mattis to increase operations in the area, although it’s not clear if it has been approved yet.

The plan would see the U.S. conducting “Freedom of Navigation Operations,” or FONOPs, within 12 nautical miles of the islands, within what China claims is its territorial waters.

Mattis signaled support for a potential increase in FONOPs during a press conference on Feb. 4 while in Japan.

“Freedom of navigation is absolute, and whether it be commercial shipping or our U.S. Navy, we will practice in international waters and transit international waters as appropriate,” he said.