Taiwan president Tsai Ing-wen pledged deeper ties with the United States at a dinner for a visiting senior State Department official, on the same day China sent 18 fighter jets to harry the island to express its anger at the trip.

China had earlier on Friday announced combat drills and denounced what it called collusion between the island, which it claims as part of its territory and the US. Taiwan scrambled its air force in response.

US Undersecretary for Economic Affairs Keith Krach arrived in Taipei...