WASHINGTON: US President Donald Trump said on Monday he believed Chinese President Xi Jinping has acted "very responsibly" with the protests in Hong Kong over an extradition bill that could see people from the territory sent to China for trial.

"We're working on trade deals right now. We'll see what happens," Trump told reporters at the White House.

Hong Kong has been hit by a series of sometimes violent protests for over two months - its most serious crisis since the city was handed back to China by Britain in 1997 but with democratic freedoms under a "one country, two systems" formula.

"I know that that's a very important situation for President Xi," Trump said, adding that "China could stop them if they wanted."

"I think that President Xi of China has acted responsibly, very responsibly." Trump told reporters. "I hope that President Xi will do the right thing."