WASHINGTON (Reuters) - China has denied a request for two U.S. Navy ships to visit Hong Kong in the coming weeks, U.S. officials said on Tuesday, as the political crisis in the former British colony deepened.

The officials, speaking on the condition of anonymity, said the transport dock ship Green Bay had requested to visit later this month, while the guided-missile cruiser Lake Erie had requested to visit in September.

One of the officials said a specific reason was not given, but such a move is not unprecedented.

The last time China denied a port visit to Hong Kong was for the assault ship Wasp in September 2018. The amphibious command ship Blue Ridge made a port visit to Hong Kong in April.

The move comes as police and demonstrators protesting against Beijing’s growing influence in Hong Kong clashed at the international airport on Tuesday after flights were disrupted for a second day.

In Washington, President Donald Trump said the Chinese government was moving troops to the border with Hong Kong and he urged calm.

Trump said the situation in Hong Kong was tricky but he hoped it would work out for everybody, including China, and “for liberty” without anyone getting hurt or killed.