For months, Taiwanese lawmakers have been fighting over a proposal by President Lai Ching-te to spend $40 billion on arms, exposing divisions in the island between a Washington-aligned president and an opposition leader leaning to Beijing. Taiwan had been under pressure from the Trump administration to increase military spending.

On Friday, Taiwan’s legislature finally approved $25 billion in special funds to buy missiles and other weapons from the United States, ending the deadlock ahead of a summit between President Trump and his Chinese counterpart.

China asserts sovereignty over Taiwan and has threatened to claim it by force. The United States provides military and political backing to Taiwan, which many in Washington see as a democratic partner against Beijing.

China’s leader, Xi Jinping, appears likely to press Mr. Trump on Taiwan during their meeting next week. He has already warned that Mr. Trump should handle U.S. arms sales to the island with “extreme caution.”

The summit, and growing pressure to lock in orders of American weapons amid high demand, may have prompted Taiwan’s rival political parties to move toward compromise on Friday.

“The clock was ticking, as there were indications that unless the legislature passed the special defense budget Taiwan would have missed an opportunity to acquire these capabilities,” said David Sacks, a fellow at the Council on Foreign Relations who had previously worked in the United States government dealing with Taiwan, including on arms sales.