China on Thursday urged the United States to return to reason after the Trump administration sought to ratchet up pressure for trade concessions by proposing a higher 25-percent tariff on $200 billion worth of Chinese imports.

U.S. Trade Representative Robert Lighthizer said on Wednesday that President Donald Trump directed the increase from a previously proposed 10 percent duty because China has refused to meet U.S. demands and has imposed retaliatory tariffs on U.S. goods.

Trump's threats of higher tariffs weighed on China's financial markets. But Chinese Foreign Ministry spokesman Geng Shuang reiterated at a regular news briefing that the United States' efforts at "blackmail" would fail.

"We would advise the United States to correct its attitude and not try to engage in blackmail. This won't work on China," Geng said.

"Secondly, we would advise the U.S. side to return to reason, and not blindly let emotions affect their decisions, because in the end this will harm themselves," Geng said.

Chinese shares fell on Thursday, and so far this year, the Shanghai Composite Index has slumped more than 16 percent, the world's second-worst performing stock index.