Beijing and Washington are keeping in "close" contact over a potential phase-one deal to resolve their trade war, China's commerce ministry said yestersday, days before another possible tariffs salvo.

Negotiators are still trying to hammer out a mini agreement, but tensions could escalate again if President Donald Trump goes through with a planned increase in import levies on Sunday.

Trump had earlier announced a 15 per cent tariff increase on $156 billion of Chinese exports to the US, due to be imposed on December 15, and there has been no word from the White House on a possible delay to that date.

The removal of tariffs is a key demand of Beijing's in the talks.

"The negotiating teams are maintaining close communication with each other," China's commerce ministry spokesman Gao Feng said at a press briefing.

He declined to comment on how China would react if a fresh round of import duties was imposed.

But China has previously said it would reimpose a 25 per cent tariff on US autos and a five per cent tariff on auto parts, starting December 15.

Beijing had lifted those tariffs earlier this year as a goodwill measure while trade talks were underway.

China's state council tariff office in August had announced punitive tariffs of five to 10 per cent on over 5,000 goods from the US worth over $75 billion, starting September 1 and December 15.

US-made mango juice, electric buses and chemical products face 10 per cent duties from December 15 while smaller aircraft, hand pumps and bearings will be hit with five per cent taxes, according to the list.