TAIPEI—Taiwan and the United States have signed their first agreement under the Biden administration, establishing a Coast Guard Working Group to coordinate policy, following China’s passing of a law that allows its coast guard to fire on foreign vessels. The new government of U.S. President Joe Biden has moved to reassure Taiwan that its commitment to the island is rock solid. The defacto Taiwanese ambassador to the United States, Hsiao Bi-khim, signed the agreement in Washington on Thursday, her office said in a statement. “It is our hope that with the new Coast Guard Working Group, both sides will forge a stronger partnership and jointly contribute even more to a free and open Indo-Pacific region.” U.S. Acting Assistant Secretary of State for East Asian and Pacific Affairs Sung Kim was at the signing ceremony, the office said. The American Institute in Taiwan, which handles U.S. ties with the island, said …