In other words, the US position on this major flash point in the Asia-Pacific region is largely unchanged although Tillerson hints at a potentially more aggressive stance when he writes: "the United States must be willing to accept risk if it is to deter further destabilising actions and reassure allies and partners that the United States will stand with them in upholding international rules and norms".

Still, this is a position with which countries in the region will be far more comfortable. The Philippines, Malaysia and Vietnam, which are all key claimants in the South China Sea territorial disputes, have been repairing relations with China in recent months in a bid to secure closer economic and financial ties.

They have no interest in a confrontation over the South China Sea. At the same time, China's investment in regional powerhouse Indonesia has doubled since 2015. And nearby Australia would also prefer its biggest trading partner and most important security ally are getting along.

In the written responses to Senator Cardin, which were initially made public by an environmental advocacy group and have since been widely circulated, Mr Tillerson also confirmed the US commitment to the One China Policy.

"Under this policy, the United States recognises the People's Republic of China as the sole legal government of China and acknowledges the Chinese position that Taiwan is part of China," he said.

"As required by the Taiwan Relations Act, the United States continues to provide Taiwan with arms of a defensive character and maintains the capacity of the United States to resist any resort to force or other forms of coercion that would jeopardise the security, or the social or economic system, of the people of Taiwan."

These comments back away from President Donald Trump's assertion the One China Policy was up for negotiation.

Tillerson's more considered written responses on the US position in Asia and Mattis' diplomatic exchanges in Japan and Korea are reassuring but there is still a great deal of uncertainty. Until it becomes clear who is in Trump's foreign policy inner circle, it is difficult to know whether their more moderate positions will be adopted.

The long-awaited phone call between Trump and Chinese President Xi Jinping will give some indication of how Sino-US relations might progress under the new US administration. But even with that call, Trump is keeping the world guessing.

Questions have been raised in China about why Xi is not among the 18 foreign heads-of-state Trump has spoken to since his inauguration more than two weeks ago.