A former US ambassador to China said he believes that the bilateral relationship, which has been built on negotiation for decades, will not be easily affected by the current tit-for-tat trade dispute.

"The trade dispute between the US and China is just a trade dispute," said J. Stapleton Roy, also and a former US assistant secretary of state, at the closing ceremony of the Harvard College China Forum at the Seaport World Trade Center in Boston on Sunday.

"We (the United States) have trade disputes, and we have traditionally had trade disputes with our close friends," Roy added, offering as an example the disagreement between the United States and Japan after the breakup of the Soviet Union in the 1980s, and the longtime rows between the US and Canada on issues such as the export of softwood lumber.

"And our relations with both Japan and Canada are stable and good," Roy said.

In his latest tweet about China on Sunday morning, US President Donald Trump wrote: "President Xi (Jinping) and I will always be friends, no matter what happens with our dispute on trade. China will take down its Trade Barriers because it is the right thing to do. Taxes will become Reciprocal & a deal will be made on Intellectual Property. Great future for both countries."

Roy said Trump's attitude "is different from yesterday".

"He was trying to coerce China into giving something on trade and didn't show interest in negotiation, but today, he changed his position," Roy said.

"So we are perhaps seeing a turnaround in the way we are going to handle the trade issue."

Roy said the dispute is "problematic because it involves economic interests of both countries in a significant way".

"But it doesn't undermine the basis for the relationship," he said.

He emphasized that negotiations built the current US-China relationship, going back to the establishment of diplomatic ties between China and the US in the 1970s.

"But people in Washington aren't even aware of it, in part because the Trump administration does not have a single person at the senior level who knows anything at all about how the US-China relationship was restored," he said.