Another senior U.S. official, speaking on condition of anonymity, said the somewhat muted U.S. response to the seizure, coupled with Trump's abandonment of the Trans-Pacific Partnership trade agreement, Philippine President Rodrigo Duterte's erratic policies and Malaysia's corruption scandal, has caused some U.S. allies to worry increasingly about the possibility of a declining American commitment to the region.
The Philippines said it was troubling that the incident took place inside its exclusive economic zone (EEZ), saying it increased the likelihood of "miscalculations that could lead to open confrontation" very near the Philippine mainland.
China is deeply suspicious of any U.S. military activities in the resource-rich South China Sea, with state media and experts saying the use of the drone was likely part of U.S. surveillance efforts in the disputed waterway.
The overseas edition of the ruling Communist Party's People's Daily said in a commentary on Monday the USNS Bowditch, which was fielding the drone and was set to pick it up, was a "serial offender" when it came to spying operations against China.
Ni Lexiong, a naval expert at Shanghai University of Political Science and Law, told Reuters he believed the Chinese navy probably had orders to take the drone.
But Ni said the incident was very different from the 2001 intercept of a U.S. spy plane by a Chinese fighter jet that resulted in a collision that killed the Chinese pilot and forced the American plane to make an emergency landing at a base on Hainan.
"This is a much smaller incident, it won't affect the overall picture of China-U.S. relations," he said, adding he did not expect China to seek an apology.
The 24 U.S. air crew members were held for 11 days before being released, souring U.S.-Chinese relations in the early days of President George W. Bush's first administration.
However, Greg Poling, a South China Sea expert at Washington's Center for Strategic and International Studies, said the U.S. military could feel compelled to take steps to further assert freedom of navigation in the region.
"For a lot of folks in the Pentagon, this over-stepped that line between legal contestation and a military threat," he said.
While the U.S. Navy under the Obama administration has sent warships periodically sailing near artificial islands claimed by China over the last year or so, it has mostly acted cautiously, seeking to avoid escalation with Beijing, which claims large swathes of the resource-rich waterway.
In October, the United States carried out a freedom of navigation operation in the South China Sea, sailing within waters claimed by China, but not within the 12-nautical-mile territorial limits of the islands.
Despite Trump's more aggressive tone, he has given no clear policy on how he plans to deal with the dispute in the South China Sea.
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