A U.S. delegation led by Sen. Tammy Duckworth (D-Ill.) is in Taipei, meeting with Taiwan officials on a previously unannounced visit.

Driving the news: Duckworth, who also visited Taiwan's capital last year as part of a COVID-19 vaccine doses donation announcement, arrived in Taipei for the three-day visit on Monday, per a Taiwan Foreign Ministry tweet.

Minister Wu held a welcome banquet for @SenDuckworth & her delegation at historic Taipei Guest House. The atmosphere was warm & conducive to rewarding talks on #Taiwan🇹🇼-#US🇺🇸 relations. We're grateful to host such good & trusted friends at a time of international uncertainty. pic.twitter.com/hRyX75OpMK

— 外交部 Ministry of Foreign Affairs, ROC (Taiwan) 🇹🇼 (@MOFA_Taiwan) May 31, 2022

Of note: Taiwan's Ministry of National Defense reported Monday that Beijing sent 30 Chinese warplanes to its air defense identification zone (ADIZ) near the island — the biggest incursion since January.

What's happening: The U.S. delegation met with Taiwan Foreign Affairs Minister Jaushieh Joseph Wu on Tuesday.

• They're scheduled to hold talks with President Tsai Ing-wen later in the day as well as Premier Su Tseng-chang and Economic Affairs Minister Wang Mei-hua before their departure Wednesday, per CNN.

The big picture: The delegation's trip follows President Biden's first visit to Japan earlier this month during which he angered China's government by saying American troops would defend Taiwan if Chinese forces attacked the self-governing island.

• Current U.S. policy acknowledges Beijing considers Taipei part of "one China," but opposes any attempts to change Taiwan's democratic status by force.

Flashback: The governments of China and Russia sent jets over the seas near Japan during Biden's visit and U.S. and Japanese forces held a joint fighter jet exercise soon after.

Editor's note: This article has been updated with details of the Chinese warplanes and with further context.