U.S. President Donald Trump meets with China's President Xi Jinping at the G20 leaders summit in Japan, June 29, 2019.

U.S. President Donald Trump said on Monday that he believed Chinese President Xi Jinping has acted "very responsibly" with the protests in Hong Kong.

For over two months, political tensions in Hong Kong have escalated over a proposed extradition bill that would allow those arrested in the territory to be sent to mainland China for trial. Hong Kong citizens are concerned that their civil rights could be slowly eroded under Beijing.

"You know, you could say what you said, but you could also say that he has allowed that to go on for a long time, and, you know, it's been relatively — I think it's been relatively non-violent," said Trump, according to a White House transcript. He was speaking to reporters at the White House before a meeting with Pakistani Prime Minister Imran Khan.

Trump added that "China could stop them if they wanted."

"I think President Xi of China has acted responsibly. Very responsibly. They've been out there protesting for a long time," Trump said. "I hope that President Xi will do the right thing."

The protests in Hong Kong have turned violent at times and is the most serious crisis since the former British colony returned to Chinese rule in 1997.

On Sunday, protesters surrounded China's main representative office in Hong Kong and defaced walls and signs. They also clashed with police.