The United States and China traded jibes as military tensions grow between the world's two largest economies, with the U.S. defense chief vowing not to "cede an inch" in the Pacific and China saying Washington was risking soldiers' lives.

Both are at loggerheads over issues from technology and human rights to Chinese military activities in the disputed South China Sea, with each accusing the other of deliberately provocative behavior.

In the latest U.S. move against China ahead of November's presidential election, Washington on Wednesday blacklisted 24 Chinese companies and targeted individuals over construction and military actions in the busy South China Sea waterway.

In Hawaii, U.S. Defense Secretary Mark Esper said Beijing is using an aggressive military modernization program in a bid to project power globally.

"To advance the CCP's agenda, the People's Liberation Army continues to pursue an aggressive modernization plan to achieve a world class military by the middle of the century," Esper said, referring to the ruling Chinese Communist Party.

"This will undoubtedly involve the PLA's provocative behavior in the South and East China Seas, and anywhere else the Chinese government has deemed critical to its interests."

However, the United States also wants to "hopefully continue to work with the People's Republic of China to get them back on a trajectory that is more aligned with the international rules based order," Esper added.

Speaking before a regional tour, Esper described the Indo-Pacific as the epicenter of a "great power competition with China."

He added, "We're not going to cede this region, an inch of ground if you will, to another country, any other country that thinks their form of government, their views on human rights, their views on sovereignty, their views on freedom of the press, freedom of religion, freedom of assembly, all those things, that somehow that's better than what many of us share."

In Beijing, China's Defense Ministry shot back at "certain U.S. politicians" it said were damaging Sino-U.S. military ties in the run-up to the November election for their own selfish gain, even seeking to create military clashes.

"This kind of behavior puts the lives of frontline officers and soldiers on both sides at risk," spokesman Wu Qian told reporters at a monthly briefing on Thursday.

China is not scared of "provocation and pressure" from the United States, and will resolutely defend itself and not allow the United States to cause trouble, he added.

"We hope the U.S. side will truly adopt a strategic vision, view China's development with an open and rational attitude, and leave behind the quagmire of anxiety and entanglement."

The tension, including China's drills this week along its coast, have sparked fears of accidental conflict, against which Taiwan President Tsai Ing-wen warned on Thursday.

On Wednesday, a U.S. defense official told Reuters that China had launched four medium-range ballistic missiles that hit the South China Sea between Hainan Island and the Paracel Islands.

On Thursday, the Pentagon said it was concerned about China's recent military exercises, including the firing of ballistic missiles.

"Conducting military exercises over disputed territory in the South China Sea is counterproductive to easing tensions and maintaining stability," the Pentagon said in a statement.

It added that the U.S. military had told Chinese authorities in July that it would continue to monitor the situation with "the expectation that the PRC (People’s Republic of China) will reduce its militarization and coercion of its neighbors in the South China Sea."