Washington: President Donald Trump has suggested that he might veto legislation designed to support anti-government protesters in Hong Kong - despite its near-unanimous support in the House and Senate - to pave the way for a trade deal with China.

Speaking on the Fox & Friends morning program on Friday, the President said that he was balancing competing priorities in the US-China relationship.

Donald Trump also claimed that he had saved the lives of thousands of Hong Kong demonstrators by telling Xi not to intervene. AP

"We have to stand with Hong Kong, but I'm also standing with President Xi [Jinping], he's a friend of mine. He's an incredible guy, but we have to stand ... I'd like to see them work it out, OK?" the President said.

"I stand with freedom, I stand with all of the things that I want to do, but we are also in the process of making one of the largest trade deals in history. And if we could do that, it would be great."

The House on Wednesday passed the Hong Kong Human Rights and Democracy Act by a vote of 417 to 1. The lone holdout was Representative Thomas Massie, a Republican from Kentucky. That came one day after the Senate had approved the measure on a unanimous vote.

Protesters have staged a daring escape from Hong Kong's besieged Polytechnic University as a tense standoff with police continues.

The veto-proof majorities indicate that Congress could overrule the President if he tries to block the bill from becoming law.

The legislation authorises sanctions on Chinese and Hong Kong officials involved in human rights abuses and requires the State Department to conduct an annual review of the special autonomous status that the US grants Hong Kong in trade matters.

The Hong Kong bill threatens to complicate trade negotiations that already are stalled on several key issues. Chinese officials have criticised the congressional action as unwanted interference in their country's internal affairs.

Trump last month announced an "agreement in principle" with China on a partial trade deal, which he hoped to sign by mid-November. But talks have deadlocked over the details of Chinese purchases of US farm products and plans for the removal of Trump's tariffs on $US360 billion ($530 billion) in Chinese goods.

Trump's comments on Friday come one day after Senator Marco Rubio, one of the authors of the Hong Kong legislation, predicted on CNBC that the President would sign the measure.

"My understanding is that they will sign it," Rubio said, referring to the White House.

A spokesman for the lawmaker, a prominent critic of the Chinese government, did not immediately respond to a request for comment.

The President also claimed, without evidence, that he had saved the lives of thousands of Hong Kong demonstrators by telling Xi not to intervene.

"The only reason he's not going in is because I'm saying it's going to affect our trade deal," Trump said.

"If it weren't for me Hong Kong would have been obliterated in 14 minutes," he said, without offering any evidence.

"He's got a million soldiers standing outside of Hong Kong that aren't going in only because I ask him please don't do it, you'll be making a big mistake, it's going to have a tremendous negative impact on the trade deal and he wants to make a trade deal."

The Washington Post, Reuters