BEIJING • China's brazen seizure of a United States Navy drone in international waters in the South China Sea has raised questions.

Diplomats and analysts said they were perplexed by the inability of the Obama administration to devise a strong response to China's challenge. It did not even dispatch an American destroyer to the spot near Subic Bay, which is still frequented by US Navy ships, some noted.

Some saw it as a taunt to President-elect Donald Trump, who has challenged the "one China" policy on Taiwan and vowed to deal forcefully with Beijing in trade and other issues.

After discussions at the National Security Council on how to deal with the issue, the Obama administration sent a demarche to China demanding the return of the drone. On Saturday, China said it would comply with the request but did not indicate when or how the equipment would be sent back.

The end result, analysts said, is that China will be emboldened by having carried out an act that amounted to hybrid warfare, falling just short of provoking conflict, and suffering few noticeable consequences.

"Allies and observers will find it hard not to conclude this represents another diminishment of American authority in the region," said Mr Douglas Paal, vice-president for studies at the Carnegie Endowment for International Peace.

Significantly, the drone was grabbed not only in international waters but also outside the "nine-dash line" that China uses as a marker for its claims in the South China Sea. In so doing, analysts said, Beijing was making the point that the entire sea was its preserve, even though it was entirely legal for the US to conduct military operations in waters within 200 nautical miles of the Philippines, an area known as an exclusive economic zone.

As China built up its navy and its submarine fleet over the past decade, it has also stressed what it calls its "inherent" right to dominate the regional seas and to challenge the presence of the US, and its allies and partners, in Asia.

The drone episode last Thursday was of a different nature and just as disquieting as past confrontations with China, analysts said.

In 2001, soon after then President George W. Bush came to office, a US spy aircraft was forced to land on Hainan Island after colliding with a Chinese fighter jet. The Chinese stripped the plane of its assets and returned its parts in boxes.

In 2009, two months after President Barack Obama took office, Chinese vessels swarmed a US Navy reconnaissance ship in what the Pentagon said were dangerous and unprofessional manoeuvres.

This time, China chose a more unconventional method to challenge the US and hastened the timetable, challenging a president-elect rather than a newly installed president as it has in the past. The drone itself, known as an unmanned underwater vehicle, was not a particularly important piece of equipment.

More important was the principle of freedom of navigation in international waters, said Dr Alexander Vuving, a specialist on Vietnam at the Asia-Pacific Centre for Security Studies in Hawaii, and whether China was in the process of imposing its own rules in the South China Sea.

"This is China showing it is in the process of setting the rules in the South China Sea, imposing its own view... and saying the South China Sea should be its own backyard," he said. "If China can get away with this incident with impunity, it will send a chilling message to countries in the region."

Some leaders, like Philippine President Rodrigo Duterte, will feel validated in a pivot away from the US towards China, Dr Vuving said.

Indeed, Manila has said it would not protest against China's moves to militarise its man-made islands in the South China Sea.

Philippine Foreign Minister Perfecto Yasay, speaking to reporters last Friday during Mr Duterte's official visit to Singapore, said the government would not issue any diplomatic protest via a "note verbale".

"We will make sure that there will be no further actions that will heighten the tensions between the two countries, particularly in the Scarborough Shoal," Mr Yasay said.

"Let them take whatever action is necessary in the pursuit of their national interest... and we will leave it at that, for the Philippines, we have our bilateral engagements with China," he added.

While Scarborough Shoal is disputed solely by China and the Philippines, several countries, including the two, have rival claims in the Spratly Islands, where China has deployed anti-aircraft and anti-missile systems on the artificial islets it built there.

Mr Yasay's remarks contrasted with those of Defence Minister Delfin Lorenzana, who last Thursday described China's latest actions in the Spratly Islands as a "big concern" for the international community.

NYTIMES, REUTERS