Donald J. Trump, the Republican presidential nominee, said that Taiwan should pay the United States for defending it from China, a remark highlighting the uncertainties — and high stakes — of how he might handle the smoldering Taiwan Strait dispute if he should win a second term.

Taiwan depends on political and military support from the United States to help resist pressure from Beijing, which claims the island as Chinese territory. Mr. Trump warned that Taiwan is perilously exposed to any attack from China and far away from U.S. protection, and signaled that he would take a more bluntly conditional approach to Taiwan.

“I think Taiwan should pay us for defense,” Mr. Trump said in an interview with Bloomberg Businessweek that published on Tuesday. “You know, we’re no different than an insurance company.”

Just as Mr. Trump’s denigration of NATO has rattled America’s allies, his comments on Taiwan raised the question of how invested a second Trump presidency would be in the island’s defense. The United States is committed by law to help Taiwan defend itself, and leaves open the possibility of sending forces if Beijing ever attacks the island.

Mr. Trump also took aim at Taiwan’s dominance in making advanced semiconductors, saying: “They did take about 100 percent of our chip business.”

The share price of Taiwan Semiconductor Manufacturing Company — the world’s biggest maker of advanced computer chips — fell by 2.4 percent on the island’s stock exchange on Wednesday, apparently in reaction to his comments.

Although Mr. Trump has made similar comments about Taiwan in recent years, his latest may land in Taiwan with a bigger impact, given his strong position in the race against President Biden.

“If I was in Taiwan, I would take this statement seriously because it is not an isolated remark — there is now a pattern,” said David Sacks, a fellow for Asia studies at the Council on Foreign Relations “This statement, in particular, epitomizes Trumpism because it reflects his purely transactional view of foreign policy.”

Taiwan already pays for nearly all of its weapons orders from U.S. manufacturers, though the Biden administration has moved to directly transfer some military equipment to Taiwan, drawing on U.S. stockpiles. Mr. Trump’s broader point seemed to be that Taiwan owed the United States more for its overall security.