A former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday for talks with the island's leaders at a time of tense relations with China.

Chris Dodd, a Democratic senator from Connecticut from 1981 to 2011, was accompanied by two former deputy secretaries of state, James Steinberg from the Democratic Obama administration and Richard Armitage, who served under Republican President George W. Bush.

The delegation will meet President Tsai Ing-wen on Thursday and exchange views with other government departments during their three-day visit, the Foreign Ministry said.

From left, former U.S. senator Chris Dodd, is greeted by Brant Christensen director of American Institute in Taiwan, center as Taiwan Foreign Minister Joseph Wu at right looks on in Taipei, Taiwan on Wednesday, April 14, 2021. The former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday at a time of tense relations with China, Taiwan's Foreign Ministry said. (Pool Photo via AP)

From left, former U.S. senator Chris Dodd, is greeted by Brant Christensen director of American Institute in Taiwan, center as Taiwan Foreign Minister Joseph Wu at right looks on in Taipei, Taiwan on Wednesday, April 14, 2021. The former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday at a time of tense relations with China, Taiwan's Foreign Ministry said. (Pool Photo via AP)

The U.S. has repeatedly expressed concern about Chinese military activity near Taiwan including frequent military flights.

Taiwan Foreign Ministry spokesperson Joanne Ou said the government welcomed the delegation from President Joe Biden's administration, whose visit “conveys the U.S.’s firm friendship and support for Taiwan."

China proposes unification with Taiwan under the “one country, two systems" model it has enforced in the former British colony of Hong Kong, virtually eliminating political opposition and strongly restricting freedom of speech. A large majority of Taiwanese favor the current system of de facto independence while maintaining close economic ties with China.

Former U.S. senator Chris Dodd, center left is followed by former U.S. Deputies Secretary of State James Steinberg and Richard Armitage as they are shown the way by Taiwan Foreign Minister Joseph Wu, center right upon arrival in Taipei, Taiwan on Wednesday, April 14, 2021. The former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday at a time of tense relations with China, Taiwan's Foreign Ministry said. (Pool Photo via AP)

Former U.S. senator Chris Dodd, center left is followed by former U.S. Deputies Secretary of State James Steinberg and Richard Armitage as they are shown the way by Taiwan Foreign Minister Joseph Wu, center right upon arrival in Taipei, Taiwan on Wednesday, April 14, 2021. The former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday at a time of tense relations with China, Taiwan's Foreign Ministry said. (Pool Photo via AP)

The U.S. has only unofficial relations with Taiwan but is bound under American law to ensure the island can defend itself from attacks and to treat all threats against it as a matter of “grave concern." Under new legislation, the U.S. has boosted visits by Cabinet-level officials to the island and has agreed to sell upgraded missile systems, fighter jets and other defensive weaponry.

China severed formal relations with Tsai's administration and has stepped up military, diplomatic and economic pressure over her refusal to acknowledge Beijing's claim over Taiwan.

Taiwan's democratic system should not be a “barrier to unification," Ma Xiaoguang, a spokesperson for the China Cabinet's Taiwan Affairs Office, said at a new conference Wednesday.

Former U.S. senator Chris Dodd, is followed by former U.S. Deputy Secretary of State James Steinberg as they disembark upon arrival in Taipei, Taiwan on Wednesday, April 14, 2021. The former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday at a time of tense relations with China, Taiwan's Foreign Ministry said. (Pool Photo via AP)

Former U.S. senator Chris Dodd, is followed by former U.S. Deputy Secretary of State James Steinberg as they disembark upon arrival in Taipei, Taiwan on Wednesday, April 14, 2021. The former U.S. senator and two ex-State Department officials arrived in Taiwan on Wednesday at a time of tense relations with China, Taiwan's Foreign Ministry said. (Pool Photo via AP)