BEIJING >> Activity by U.S. military ships and surveillance planes directed at China has increased significantly under President Joe Biden’s administration, a spokesperson for the Chinese Defense Ministry said Thursday.

As an example, Wu Qian said the Navy destroyer USS Mustin recently conducted close-in observation of the Chinese aircraft carrier Liaoning and its battle group.

That had “seriously interfered with the Chinese side’s training activities and seriously threatened the safety of navigation and personnel on the both sides,” Wu said. The ship was warned to leave and a formal protest was filed with the U.S., he said.

Activity by U.S. military ships was up 20% and by planes 40% in Chinese-claimed areas since Biden took office in January over the same period last year, Wu said.

“The U.S. frequently dispatches ships and planes to operate in seas and airspace near China, promoting regional militarization and threatening regional peace and stability,” Wu said at a monthly briefing held virtually.

China routinely objects to the U.S. military presence in the South China Sea, which it claims almost in its entirety, as well as the passage of Navy ships through the Taiwan Strait.

The country recently marked the 20th anniversary of the collision between a U.S. surveillance plane and a Chinese navy fighter near the Chinese island province of Hainan that resulted in the Chinese pilot’s death. He was called a hero who sacrificed himself for the defense of the motherland. The U.S. says its plane was in international airspace and the accident was the result of reckless flying by the Chinese side.

Wu also blasted moves to beef up monitoring of Chinese aircraft movements by Taiwan, the self-governing island democracy claimed by China as its own territory, to be annexed by force if necessary.

Efforts by Taiwan’s government to stave off what China refers to as inevitable unification are like “a mantis trying to stop a chariot,” Wu said.

The U.S. maintains only unofficial relations with Taiwan in deference to Beijing, but provides the island with defensive weapons and is legally bound to treat threats to it as matters of “grave concern.” Increased activity by the Chinese military around Taiwan has been raising concern about the possibility of a conflict.

In an interview with Britain’s Sky News, Taiwan Foreign Minister Joseph Wu reiterated recent warnings that the military threat from China is growing through “misinformation campaigns, hybrid warfare, and … grey zone activities.”

“And all these seem to be preparing for their final military assault against Taiwan,” Wu told Sky.

“This is our country, this is our people and this is our way of life. We will defend ourselves to the very end,” Wu said.

Biden did not address such military threats in his address to Congress on Wednesday night, instead emphasizing that China and others were “closing in fast” in economic and technological terms.

“We’re in a competition with China and other countries to win the 21st century,” Biden said.

That drew a harsh response from China’s Foreign Ministry, reflecting how hopes for an improvement in the tone, if not the substance, of relations under Biden have born little fruit.

“The U.S. always demands that others follow the rules while violating the rules themselves,” spokesperson Wang Wenbin said at a daily briefing.

“It is in nature out of Cold War thinking and ideological bias, and is a sign of lack of self-confidence,” Wang said. “We hope the U.S. can discard the mentality of sour grapes towards China.”