As political unrest in Hong Kong has continued unabated and China has shown no sign of acceding to protesters' demands, the administration of Prime Minister Shinzo Abe is facing mounting pressure to rescind its invitation to President Xi Jinping for a state visit next spring.

U.S. President Donald Trump's approval this week of a bill in support of Hong Kong's pro-democracy protesters was the latest move that could ultimately put the heat on Tokyo over its warming ties with Beijing. A Japanese government source said Abe, who has tried to build a personal rapport with Trump, could struggle to obtain U.S. understanding about Xi's state visit here at a time when Washington and Beijing are also divided over trade and security issues.

"Relations between Japan and China have been certainly improving, but they are still fragile," the source said, adding, "Possible U.S. involvement in Hong Kong would further complicate Japan's stance on how to get along with China."