President Lai Ching-te of Taiwan on Thursday sought to reassure his citizens that a plan by a Taiwanese chip giant to spend $100 billion in the United States would benefit the island, after the company’s pledge this week raised concerns at home.

Taiwan Semiconductor Manufacturing Company, the world’s largest chip manufacturer, announced on Monday that over the next four years it would expand its operations in Arizona to make chips for artificial intelligence and other high-tech applications. President Trump has pressed Taiwan to loosen its dominance in advanced semiconductors and to move production to the United States, and he has warned of hefty tariffs if his demands are not met.

But TSMC’s announcement also stirred debate and misgivings in Taiwan, a democratically governed island where many people see the chip sector as a vital economic pillar and a shield against possible aggression by China, which claims it is part of its territory. The commitment from TSMC would lift its planned spending in the United States to $165 billion, more than double its previous commitments there.

Mr. Lai, in a news conference in Taipei on Thursday with C.C. Wei, the chief executive of TSMC, asserted that the plan was good for TSMC, Taiwan and the United States.

“We have seen every time that with each initiative by TSMC, TSMC has grown even stronger and more competitive, while also providing Taiwan’s businesses with opportunities for international cooperation and contributing to Taiwan’s greater strength,” Mr. Lai told reporters at the presidential office. He said that Taiwan could now “confidently cross the Pacific Ocean and expand eastward to the American continent.”