The U.S. Navy’s Theodore Roosevelt Carrier Strike Group joined the Nimitz Carrier Strike Group on Tuesday for rare dual aircraft carrier exercises involving the massive Nimitz-class warships alongside accompanying vessels and aircraft.

It was the first time two aircraft carriers trained together in the South China Sea since July, and the first time the two groups involved joined forces since June, when they conducted joint operations in the Philippine Sea.

The naval commanders involved praised the exercise.

Navy Rear Admiral Doug Verissimo, commander of the USS Theodore Roosevelt’s Carrier Strike Group Nine, said the maneuvers “ensure that we are tactically proficient to meet the challenge of maintaining peace and we are able to continue to show our partners and allies in the region that we are committed to promoting a Free and Open Indo-Pacific.”

His counterpart on the USS Nimitz, Navy Rear Admiral Jim Kirk, said the drills contributed to “regional stability and security,” and demonstrated the U.S. Navy was “committed to ensuring the lawful use of the sea that all nations enjoy under international law.”

But in Beijing, the display was perceived as a stark challenge from a new president looking to disrupt peace and take on the People’s Republic.

“The United States frequently sent vessels and aircraft to the South China Sea to flex its muscles,” Chinese Foreign Ministry spokesperson Wang Wenbin told reporters. “This is not conducive to peace and stability in the region.”

He warned the U.S. that the People’s Liberation Army was capable of responding to any threats.

“China will continue to take necessary measures to firmly defend national sovereignty and security and work together with regional countries to safeguard peace and stability in the South China Sea,” Wang said.

The exchange comes less than a week after the U.S. Navy sent Arleigh Burke-class guided-missile destroyer USS John McCain through the disputed Taiwan Strait in a move that angered China, which dispatched PLA forces to intercept the warship as it later sailed near the contested Paracel Islands also claimed by Vietnam.

Air Force Senior Colonel Tian Junli, spokesperson for the PLA Southern Theater Command, blasted the move at the time.

“The US move is a repeat of its old trick to manipulate the cross-Strait situation in mixed ways, which has seriously violated China’s sovereignty and security, gravely undermined regional peace and stability, and deliberately disrupted the good atmosphere of peace, friendship and cooperation in the South China Sea,” Tian said in a statement published Friday by the Chinese Defense Ministry.

He then proceeded to declare China alone had dominion over the contested land formations dotting the massive South China Sea

“China has indisputable sovereignty over the islands in the South China Sea and their adjacent waters,” he said, “and the troops of the PLA Southern Theater Command will always stay on high alert, firmly perform their duties and missions to safeguard China’s sovereignty and security and protect peace and stability in the South China Sea.”

PLA jets have continually entered Taiwan’s self-proclaimed Air Defense Identification Zone. This boundary is unrecognized, along with other Taiwanese claims of sovereignty, by China, which seeks to reunify the two, by force if necessary.

Even as rhetorical tensions run high, a Navy spokesperson said that the situation surrounding the South China Sea and the greater region remains roughly the same since Biden took office.

“The U.S. has a persistent military presence and routinely operates throughout the Indo-Pacific, including the waters and airspace surrounding the East China Sea and South China Sea, just as we have for more than a century,” a Navy spokesperson told Newsweek. “The vast majority of U.S. military interactions with the PLA, not just in the South China Sea but throughout the region, are safe and in accordance with international norms.”

The spokesperson cautioned against efforts to misrepresent the U.S. mission.

“Attempts to misconstrue or sensationalize our operations are irresponsible and counterproductive,” the spokesperson said. “The U.S. will continue to fly, sail and operate wherever international law allows in accordance with international norms and our agreements.”

While the new administration has publicly rejected much of its predecessor’s foreign policies, Biden and his officials have endorsed some of former President Donald Trump’s assertive moves against China, including in the high-traffic and resource-rich South China Sea, and also in affirming support for Taiwan.

“I think in fairness to President Trump he was right to take a tougher approach to China,” Secretary of State Antony Blinken said during a CNN interview Monday. “That was the right thing to do. The way he went about it, in my judgment, was wrong across the board, but the basic principle was the right one.”

He said there would be areas of agreement and disagreement between the top two powers, but that ultimately Washington sought to maintain the upper hand in the relationship.

“We have to engage China from a position of strength,” Blinken said. “And whether it’s the adversarial aspects of the relationship, the competitive ones, or the cooperative ones which are there in our mutual interest, we have to deal with it from a position of strength.”

Blinken spoke Friday with Chinese Communist Party Central Foreign Affairs Commission Director Yang Jiechi, but since taking office on Jan. 20, Biden has yet to speak with his counterpart President Xi Jinping.

In an interview with CBS News on Friday, Biden discussed his history with Xi, whom he met while vice president under former President Barack Obama. Biden said the two would have “a whole lot to talk about” when they managed to arrange their first conversation.

“He very bright, he’s very tough,” Biden said. “He doesn’t have—and I don’t mean this is a criticism, just the reality—he doesn’t have a democratic, small ’d,’ bone in his body,” Biden said. “The question is, I’ve said to him all along that we need not have a conflict, but there’s going to be extreme competition.”

Responding to these remarks, Wang told Monday’s press conference that “China is committed to developing a relationship with the United States featuring no confrontation, no conflict, mutual respect and win-win cooperation.”

But he added a qualification, stressing “national sovereignty.”

“At the same time, we will firmly safeguard national sovereignty, security and development interests,” Wang said. “The two sides should work in the same direction, focus on cooperation and manage differences to promote the sound and steady development of bilateral ties and better serve the people of both countries and beyond.”