Krach, who arrived in Taipei on Thursday afternoon, is in Taiwan for a memorial service on Saturday for former president Lee Teng-hui, who was revered by many on the island and internationally as the father of Taiwan's democracy.

Krach is expected to meet Taiwan President Tsai Ing-wen on Friday.

His visit follows one last month by US Health Secretary Alex Azar, the highest-level US official to go to the democratic island in four decades.

Speaking in Beijing, Chinese foreign ministry spokesman Wang Wenbin said China has lodged "stern representations" with Washington about Krach's trip and it opposed any official exchanges between the United States and Taiwan.

The visit would give succour to the forces of Taiwan independence and damage Sino-US ties, Wang said.

"We urge the US side to fully recognise the extreme sensitivity of the Taiwan issue," Wang said. "China will make a necessary response depending on how the situation develops."

He did not give details.

Relations between China and the United States have nosedived in recent months, with disagreements over Taiwan, trade, human rights, the coronavirus pandemic and other issues.

China views Taiwan's president as a dangerous separatist. She says the island is already an independent country called the Republic of China, Taiwan's formal name.

Krach is also likely to hold at least some form of trade talks during his trip, though details have not been announced.

Australian Associated Press