WASHINGTON: The new US administration of President Donald Trump vowed on Monday that the United States would prevent China from taking over territory in international waters in the South China Sea, something Chinese state media has warned would require Washington to "wage war."

The comments at a briefing from White House spokesman Sean Spicer signaled a sharp departure from years of cautious US handling of China's assertive pursuit of territory claims in Asia, just days after Trump took office on Friday.

"The US is going to make sure that we protect our interests there," Spicer said when asked if Trump agreed with comments by his secretary of state nominee, Rex Tillerson, on January 11 that China should not be allowed access to islands it has built in the contested South China Sea.

"It’s a question of if those islands are in fact in international waters and not part of China proper, then yeah, we’re going to make sure that we defend international territories from being taken over by one country," he said.

Tillerson's remarks at his Senate confirmation hearing prompted Chinese state media to say the United States would need to "wage war" to bar China's access to the islands where it has built military-length air strips and installed weapons systems.

Tillerson was asked at the hearing whether he supported a more aggressive posture toward China and said: "We’re going to have to send China a clear signal that, first, the island-building stops and, second, your access to those islands also is not going to be allowed.”

The former Exxon Mobil Corp chairman and chief executive did not elaborate on what might be done to deny China access to the islands.

But analysts said his comments, like those of Spicer, suggested the possibility of US military action, or even a naval blockade, that would risk armed confrontation with China, an increasingly formidable nuclear-armed military power. It is also the world's second-largest economy and the target of accusations by Trump that it is stealing American jobs.

Spicer declined to elaborate when asked how the United States could enforce such a move against China, except to say: “I think, as we develop further, we’ll have more information on it.”

Tillerson narrowly won approval from a Senate committee on Monday and is expected to win confirmation from the full Senate.

RISK OF DANGEROUS ESCALATION

Military experts said that while the US Navy has extensive capabilities in Asia to stage blockading operations with ships, submarines and planes, any such move against China's growing naval fleets would risk dangerous escalation.

Aides have said that Trump plans a major naval build-up in East Asia to counter China's rise.

China's embassy in Washington did not immediately respond to a request for comment on the White House remarks.

China's Foreign Ministry said earlier this month it could not guess what Tillerson meant by his remarks, which came after Trump questioned Washington's longstanding and highly sensitive "one-China" policy over Taiwan.

Washington-based South China Sea expert Mira Rapp-Hooper at the Center for a New American Security called the threats to bar China's access in the South China Sea "incredible" and said it had no basis in international law.

"A blockade - which is what would be required to actually bar access - is an act of war," she added.

"The Trump administration has begun to draw red lines in Asia that they will almost certainly not be able to uphold, but they may nonetheless be very destabilizing to the relationship with China, invite crises, and convince the rest of the world that the United States is an unreliable partner."

Bonnie Glaser at the Center for Strategic and International Studies think tank called Spicer's remarks "worrisome" and said the new administration was "sending confusing and conflicting messages."

Dean Cheng, a China expert at the conservative Heritage Foundation, said Spicer's remarks showed the South China Sea was an important issue for the Trump administration.

He said it was significant that neither Spicer nor Tillerson had been specific as to what actions would be taken and this left open the possibility that economic measures - instead of military steps - could be used against China and firms that carry out island building.