TAIPEI, Taiwan — President Tsai Ing-wen of Taiwan welcomed American dignitaries on Wednesday in the face of rising tensions with China, saying the self-ruled island needed to protect itself “from new, sophisticated threats coming from across the strait.”

Ms. Tsai made the remarks at a dinner at the American Chamber of Commerce in Taipei in honor of the 40th anniversary of the Taiwan Relations Act, the law that has guided the United States’ unofficial relationship with the island’s government. The dinner was but the latest round of signaling of Washington’s resolve to stand by Taiwan as tensions mount with Beijing.

In the past two weeks, Washington, Taipei and Beijing have traded words over Chinese jet incursions, Taiwan’s requests for American-made fighter jets, the American military presence in its unofficial embassy in Taipei, and Ms. Tsai’s recent stop in Hawaii.

“We must make sure Taiwan’s economic and security position remains on the right track,” Ms. Tsai told a group largely comprising American businesspeople, emphasizing the need to continue diversifying Taiwan’s economy from reliance on mainland China.