US President Donald Trump has urged his Chinese counterpart Xi Jinping to meet protesters in Hong Kong who have been demanding democratic reforms. Hong Kong has been in turmoil for weeks, with protesters causing chaos at the airport earlier this week. Mr Trump had previously appeared to suggest that he himself should meet Mr Xi to discuss the crisis in the city. Millions of Hong Kong citizens have taken part in 10 weeks of anti-government protests. Also on Thursday, the Chinese ambassador to the UK warned that Beijing would intervene in Hong Kong if events deteriorated further. He said the territory was facing its gravest situation since it was handed back from the UK to China in 1997. The tumultuous pro-democracy protests were sparked by opposition to a bill that would have allowed extraditions from Hong Kong to mainland China. In an earlier tweet, Mr Trump said he had "ZERO doubt" that Mr Xi could "humanely solve the Hong Kong problem". He also tied the protests to a US trade deal with Beijing, in the face of ongoing trade tensions. "Of course China wants to make a deal. Let them work humanely with Hong Kong first!" he tweeted. The controversial extradition bill has now been suspended, but the protests have evolved into a broader movement, with demonstrators expressing anger at alleged police brutality, and demanding democratic reform. Hong Kong, a former British colony, is part of China under a "one country, two systems" model that grants it a high level of autonomy. It has its own legal system and judiciary and enjoys certain freedoms not seen in the mainland - Hong Kong and Macau for example, are the only places in Chinese territory where people can hold vigils commemorating the 1989 Tiananmen Square crackdown.