A spokeswoman for China's Foreign Ministry said on Thursday that "there are no winners in a tariff war" in response to Washington's latest threat of slapping tariffs on any country supplying weapons to Iran.

United States President Donald Trump said on Wednesday that the US is in talks with Iran over "tariff and sanctions relief", while also threatening 50-percent tariffs on any country supplying weapons to Tehran.

"China's position is very clear: there are no winners in a tariff war," Mao Ning said at Thursday's news conference in Beijing.

Responding to another question on the Middle East situation, Mao said China has consistently called for an immediate ceasefire and an end to military action, resolving disputes through political and diplomatic channels, and ultimately achieving lasting peace and stability in the Middle East and the Gulf region.

"We hope all parties will properly resolve their differences through dialogue and negotiations, and China will continue working toward easing tensions and bringing an end to the fighting," she said.