Washington cut diplomatic ties with Taipei in 1979 but remains the island’s strongest ally and sole foreign arms supplier.
It opened the American Institute of Taiwan (AIT) to conduct relations between the two sides after severing ties.
The new complex, a significant upgrade from the low-key military building the AIT had used for decades, will serve as the representative office later this summer, said AIT director Kin Moy.
Marie Royce, US Assistant Secretary of State for Educational and Cultural Affairs, and US Congressman Gregg Harper are expected to attend Tuesday’s ceremony.
Ms Royce is the highest-ranking State Department official to visit Taiwan since 2015.
China claims Taiwan under its “one China” policy and Beijing has never renounced the use of force to bring what it sees as a wayward province under its control.
China’s hostility towards Taiwan has grown since President Tsai Ing-wen was elected in 2016. Beijing suspects Ms Tsai wants to push for formal independence, which would cross a red line for Communist Party leaders in Beijing.
Ms Tsai, who has said she wants to maintain the status quo, but will protect Taiwan’s security and not be bullied by Beijing, is expected to give a speech at the new AIT office on Tuesday.
Widely read Global Times, run by the Chinese Communist Party’s official People’s Daily, said on Tuesday that China needed to warn Taiwan and the United States against provocation.
“The mainland must continue to build up its deterrence against Taiwanese authorities, making them know that the US cannot be their saviour,” it said in an editorial on the opening of the new office.
Taiwan recently lost two diplomatic allies which switched ties to China, while some international companies have changed their websites to show the island’s designation as being part of China.
China has also stepped up military drills, sending bombers and jet fighters on exercises near the island that Taipei has denounced as intimidation.