Trump said after a G7 summit of world leaders in Biarritz, France, that he believed China was sincere about wanting to reach a deal, citing what he described as increasing economic pressure on Beijing and job losses there.

Chinese Vice Premier Liu He, who has been leading the talks with Washington, said on Monday China was willing to resolve the trade dispute through "calm" negotiations and opposed any increase in trade tensions.

Trump cited Liu's comments as a positive sign, underscoring his seniority, and repeated his assertion that Chinese officials had contacted US trade counterparts overnight and offered to resume negotiations, a claim China declined to confirm.

"I think they want to make a deal very badly. I think that was elevated last night. The vice chairman of China came out, he said he wants to see a deal made," Trump said.

"The longer they wait the harder it is to put back, if it can be put back at all," Trump said at a news conference on Monday with French President Emmanuel Macron. "I don't think they have a choice."

Macron said an agreement would help dispel uncertainty that has been weighing on global markets. He said Trump had told other G7 leaders that he wanted to strike a deal with China.

Trump said he was more upbeat about the prospects for an agreement than in the recent past.

Days after referring to President Xi Jinping as an enemy, Trump heaped praise on his Chinese counterpart in separate remarks twice on Monday, alternately calling him a "great leader" and a "brilliant man".

In Beijing, foreign ministry spokesman Geng Shuang said he had not heard that a phone call between the two sides had taken place. However, China's commerce ministry typically releases statements on trade calls. It did not respond to a request for comment.

When pressed on whether a call had taken place, Trump emphasised Liu's comments. US Treasury Secretary Steven Mnuchin said there had been contact between the two sides but declined to say with whom.

Hu Xijin, editor of the state-controlled Global Times newspaper, tweeted: "Based on what I know, Chinese and US top negotiators didn't hold phone talks in recent days. The two sides have been keeping contact at technical level, it doesn't have significance that President Trump suggested. China didn't change its position. China won't cave to US pressure."

The increasingly bitter trade war between the world's two largest economies worsened on Friday with both sides levelling more tariffs on each other's exports.

Trump announced an additional duty on some $US550 billion ($A813 billion) of targeted Chinese goods, hours after China unveiled retaliatory tariffs on $US75 billion worth of US goods.

On Sunday, the White House said Trump regretted not raising the tariffs even more. But Trump also appeared to back off of his threat to order US companies out of China.

Liu, Xi's top economic adviser said at a conference in southwestern Chongqing: "We are willing to resolve the issue through consultations and co-operation in a calm attitude and resolutely oppose the escalation of the trade war.

"We believe the escalation of the trade war is not beneficial for China, the United States, nor to the interests of the people of the world."

The trade war has damaged global growth and raised market fears the world economy will tip into recession.

The Chinese foreign ministry spokesman said China would retaliate if Trump enforced the latest US tariffs.

The two sides were due to meet in September in Washington but it was unclear whether the new tariff tit-for-tat would alter those plans.

Australian Associated Press