US President Donald Trump is "optimistic" about striking a trade deal with China, the White House said on Friday, as China responded to the United States' "reciprocal tariffs" by increasing its additional tariffs on US goods from 84 percent to 125 percent.

"The president has made it very clear he's open to a deal with China," White House Press Secretary Karoline Leavitt told reporters, adding that "he's optimistic."

Asked to comment on Leavitt's remarks, a Chinese Embassy spokesperson referred China Daily to the Foreign Ministry's statement.

At a regular news conference on Friday, Foreign Ministry spokesperson Lin Jian said, "If the US truly wants to resolve the issue through dialogue and negotiation, it should stop maximum pressure and capricious and destructive behavior."

"This never works with China. For any dialogue to happen, they must be based on equality, respect and mutual benefit. If the US is determined to fight a tariff and trade war, China's response will continue to the end," he said.

China's latest countermeasures, effective on Saturday, followed the US move to raise the "reciprocal tariffs" on Chinese imports to 125 percent on Thursday.

The Economist, in a report on Thursday, said "Trump's incoherent trade policy will do lasting damage", adding that "even after his backtracking, the president has done profound harm to the world economy."

Former US Treasury Secretary Janet Yellen said she agreed with the Economist's view and called Trump's trade policy "the worst self-inflicted wound" in an interview with CNN on Thursday.

She said the tariffs imposed on China are "prohibitive".

"They're going to result in massive impacts on the United States and the global economy. No one knows where these policies are headed," Yellen told CNN.