A top Republican lawmaker will lead a US congressional delegation to Taiwan in August, the Financial Times reports.

The visit by Roger Wicker, a Republican Senator from Mississippi and chair of the Senate armed services committee, was confirmed by three people familiar with the plans. Wicker is one of Taiwan’s biggest allies in Congress.

Wicker’s office declined to comment.

The visit comes at a delicate point in US-Taiwan relations. There is rising concern in Washington and Taipei that the US president may be less willing to help Taiwan as he pushes for a summit with China’s President Xi Jinping. Beijing claims sovereignty over Taiwan and has not ruled out using force to take it.

Taipei is concerned that Trump will sacrifice its interests to placate Beijing as he tries to secure a summit with Xi in the autumn and as US and Chinese negotiators continue talks to reach a trade deal.

Officials in Taiwan are also nervous because Taipei has failed to secure a trade deal with Washington.