China, which views Taiwan as its own territory, has stepped up military and political pressure over the past three years to try and force the island to accept Beijing’s sovereignty claims, which the government in Taipei strongly rejects.

Taiwan will hold presidential and parliamentary elections in January, with Lai, the ruling Democratic Progressive Party’s (DPP) presidential candidate, the frontrunner in most opinion polls.

Lai is making what are officially stopovers in the US on his way to and from Paraguay for the Aug 15 inauguration of its new president, drawing anger from Beijing which slammed Lai as a separatist.

Chinese ambassador Xie Feng told the Aspen Security Forum that “Taiwan is China’s Taiwan” and that the country wanted a peaceful “reunification”, but Taiwanese “separatists” were advancing their agenda, seeking US support.

“They even do not admit they are Chinese. So this is a very dangerous path they are taking,” Xie said.

Provocative moves by Taiwan “separatists” should be contained, he added.

“Now the priority for us is to stop Lai Ching-te from visiting the US, which is like a grey rhino charging at us,” Xie said, using Lai’s Chinese language name.

A “grey rhino” event refers to a highly obvious yet ignored threat.

Taiwan president Tsai Ing-wen and her government have repeatedly offered talks with China but been rejected, as Beijing views them as separatists. Both Tsai and Lai say only Taiwan’s people can decide their future.

The top US diplomat in Taipei said on Wednesday that there was no reason for China to take “provocative” action in response to Lai’s stop overs in the US and that such transits have happened for many years and are routine.

In August and then again in April, China staged large-scale war games around Taiwan, angered by the August visit to Taiwan of then-US House Speaker Nancy Pelosi and in April by Taiwan president Tsai Ing-wen meeting current House Speaker Kevin McCarthy in Los Angeles, while she was transitting back from a visit to Central America.