BEIJING — China’s seizure of an American underwater drone is the latest sign that the Pacific Ocean’s dominant power and its rising Asian challenger are headed for more confrontation once U.S. President-elect Donald Trump takes office, analysts said today.

Chinese political experts said China seized the glider in the South China Sea last week to send a strong warning to Trump not to test Beijing’s resolve over the sensitive issue of Taiwan, the self-ruled island Beijing considers part of its territory. Meanwhile, smaller countries in Southeast Asia are watching the back-and-forth closely for signs that U.S. naval dominance might be diminishing, others said.

Trump’s Dec. 2 phone call with Taiwanese President Tsai Ing-wen was the first time an American president or president-elect has publicly spoken to Taiwan’s leader since Washington broke off its formal diplomatic relationship in 1979 at China’s behest. Trump later said he did not feel “bound by a one-China policy” unless the U.S. could gain trade or other benefits from China. Beijing regards any acknowledgement that Taiwan has its own head of state as a grave insult.

The drone seizure “is a kind of response from China to Trump’s recent provocations on the issue,” said Ni Lexiong, a military expert at the Shanghai University of Political Science and Law. “It can be regarded as a warning to countries such as the U.S. and Japan on their attempts to challenge China’s core interests.”

The Pentagon said a Chinese ship seized the U.S. drone Thursday afternoon in an area about 57 miles northwest of Subic Bay near the Philippines. Several U.S. analysts say the seizure occurred inside the exclusive economic zone of the Philippines, which would appear to violate international law.

China’s defense ministry said its navy seized the underwater glider to ensure the safety of passing ships and that it would turn over the device using unspecified “appropriate means.” Chinese foreign ministry spokeswoman Hua Chunying today reiterated the defense ministry’s objections to what she called U.S. “reconnaissance and surveys in Chinese waters.”

China claims almost the entire South China Sea as its own with a roughly drawn border known as the “nine-dash line” running along western Philippine islands. Even as an international tribunal in June largely rejected China’s expansive claims, the Chinese military continues to run naval patrols and training flights over disputed islands in the area as well as the adjoining East China Sea.