TAIPEI, 19 September 2020: A top US diplomat landed in Taiwan on Thursday, angering China as Washington sent its highest-ranking State Department official in 40 to the self-ruled island.

Keith Krach, undersecretary of state for economic growth, energy and the environment, is visiting to attend a memorial service for late president Lee Teng-hui on Saturday, the US State Department said.

The trip, the second high-ranking US visit in as many months, sparked an immediate rebuke from China, which baulks at any recognition of Taiwan and has mounted a decades-long policy of marginalising the democratic island.

Beijing considers Taiwan part of its territory, to be absorbed into the mainland -- by force if necessary.

"China strongly opposes this," foreign ministry spokesman Wang Wenbin told reporters Thursday, saying the trip "encourages the arrogant attitude of Taiwan independence separatist forces".

Relations between the United States and China are at their lowest point in decades, with the two sides clashing over a range of trade, military and security issues, as well as the coronavirus pandemic.

Washington´s increased outreach to Taiwan under US President Donald Trump has become yet another flashpoint between the two powers.

"The United States honours President Lee´s legacy by continuing our strong bonds with Taiwan and its vibrant democracy through shared political and economic values," spokeswoman Morgan Ortagus said in a statement announcing Krach´s trip.

Taiwan´s foreign ministry said Krach, accompanied by assistant secretary Robert Destro, would also discuss "how to strengthen bilateral economic cooperation" during his three-day visit.

It described him as the highest-ranking State Department official to visit Taiwan since 1979, when Washington switched diplomatic recognition to Beijing from Taipei.

Taiwan President Tsai Ing-wen will host a dinner for the US delegation on Friday.

"We look forward to more exchanges and discussions between Taiwan and the US to solidify the foundation for further collaborations, including economic cooperation, through undersecretary Krach´s visit," her office said in a statement.