"I hope they're going to be able to work it out with China," Trump told reporters at the White House, as Hong Kong was rocked by the worst political violence since its handover to China.

"I understand the reason for the demonstration," he said. "I hope it all works out for China and for Hong Kong."

Trump's cautious response to what he said were "massive" demonstrations came as Washington and Beijing try to pick up the pieces of their collapsed talks on resolving a trade war.

"We're doing very well with respect to China," Trump said, referring to huge trade tariffs imposed on Chinese imports.

Trump reiterated that he expects to meet President Xi Jinping at a G20 summit later this month.

"I have a feeling that we're going to make a deal with China," he said.