China will not hesitate to fight back if the United States escalates its trade spat with Beijing, the commerce ministry said on Thursday, asserting that Chinese President Xi Jinping's pledge to cut import tariffs is not a concession to Washington.

Xi on Tuesday vowed to open China's economy further and lower import duties on goods such as cars. U.S. President Donald Trumpresponded in a tweet saying he was "thankful" for Xi's kind words on tariffs and access for U.S. automakers, as well as his "enlightenment" on intellectual property issues.

Washington is accusing Chinese firms of stealing the trade secrets of U.S. companies and forcing them into joint ventures to acquire their technology — the crux of Trump's current tariff threats against China.

It would be misleading to say Xi's pledge this week was a concession to the United States, commerce ministry spokesman Gao Feng said at a regular press briefing in Beijing.

Xi was merely outlining China's strategy to open up further, which had nothing to do with its trade friction with the United States, Gao said.

Trump on Monday criticized China on Twitter for maintaining 25 percent import tariffs on autos compared to the United States' 2.5 percent duties, calling such a relationship with China not free trade but "stupid trade."

Gao said it is not reasonable to require tariffs to be completely equal for both sides, and that there is no demand for tariff equalization in bilateral relationships under World Trade Organization rules.

China and the U.S. have not held any negotiations on their bilateral trade frictions, Gao said, adding that it is not a matter of whether Beijing is willing to negotiate with Washington. It's about the United States not showing sincerity, he said.