China will be forced to retaliate if the United States implements any new tariff measures, China's commerce ministry warned on Thursday, as the world's two biggest economies remain locked in an intensifying trade war.

Global markets were on edge after U.S. President Donald Trump threatened fresh tariffs on another $200 billion in Chinese imports.

"If the United States, regardless of opposition, adopts any new tariff measures, China will be forced to roll out necessary retaliatory measures," ministry spokesman Gao Feng told a regular news conference.

China will closely monitor the impact from any fresh tariffs and adopt strong measures to help Chinese or foreign firms operating in China to overcome difficulties, said Gao.

The Trump administration is ready to move ahead with a next round of tariffs after a public comment period ends at midnight in Washington on Thursday, but the timing is uncertain, people familiar with the administration's plans told Reuters.

The new duties will start to hit consumer products directly, including furniture, lighting products, tires, bicycles and car seats for babies.

China and the United States have already slapped tit-for-tat tariffs on $50 billion of each other's goods, spooking financial markets in recent months as investors and policy makers worried the bitter trade war could derail global growth.

Trump is demanding Beijing improve market access and intellectual property protections for U.S. companies, cut industrial subsidies and slash a $375 billion trade gap.

Markets fear any fresh U.S. duties on Chinese imports will mark a major escalation in the trade dispute between the world's two economic giants, potentially causing significant drag on global business investment, trade and growth.

In August, China unveiled a proposed list of retaliatory tariffs on $60 billion of U.S. goods ranging from liquefied natural gas to certain types of aircraft, in response to the U.S. measures.

Trump said on Wednesday that the United States was not yet ready to come to an agreement over trade disputes with China but he said talks would continue.