WASHINGTON, Sept 3 (Reuters) - U.S. President Joe Biden will host leaders of Pacific Island nations at a Sept. 28-29 gathering in Washington, the White House said on Friday, the latest U.S. effort to step up ties with the region increasingly courted by China.

The summit will reflect the United States' "broadening and deepening cooperation on key issues such as climate change, pandemic response, economic recovery, maritime security, environmental protection, and advancing a free and open Indo-Pacific," the White House said in a statement.

An administration official told Reuters the White House had invited 12 Pacific Islands countries, including the Solomon Islands, which in April struck a security pact with China, heightening Washington's concern about Beijing's growing influence.

The Solomon Islands, which switched its ties to Beijing from Chinese-claimed Taiwan in 2019, is a focal point in the escalating competition between China and the United States in the strategically vital region.

The Federated States of Micronesia, Kiribati, Papua New Guinea, Vanuatu, Samoa, Tonga, and Fiji were also invited, as well as the Marshall Islands, Nauru, Palau, and Tuvalu, which Taiwan counts among its 14 diplomatic allies.

Tuvalu Prime Minister Kausea Natano arrived in Taipei on Saturday for a week-long trip and will sign an agreement reaffirming diplomatic ties with Taiwan, the Taiwanese Foreign Ministry said.

Natano, whose country this month marks 43 years of ties with Taiwan, will meet President Tsai Ing-wen on Monday.

The White House did not provide details on which countries had confirmed attendance for the summit, which had been signaled as a priority by U.S. Deputy Secretary of State Wendy Sherman during a trip to the region in August.

During that trip, Solomon Islands Prime Minister Manasseh Sogavare skipped a planned appearance with Sherman at a World War Two commemoration, and later that month his government did not respond to a U.S. Coast Guard vessel's request to refuel.

The United States has stepped up engagement with Pacific Islands countries under Biden, sending several senior official delegations and announcing plans to open embassies in the Solomon Islands, Kiribati, and Tonga.