The United States has "enduring" interests in the Asia-Pacific region and is working for an orderly transfer of power to the administration of President-elect Donald Trump, U.S. Defense Secretary Ash Carter said on Wednesday.

Carter is in Japan to try to soothe anxieties caused by the victory of Trump, who has called for allies to pay more to sustain U.S. forces, or face their possible withdrawal.

The outgoing administration of Barack Obama made Asia and U.S. alliances there a top priority. Details of Trump's approach to the region remain scant, but he wants to see key U.S. allies, such as Japan and South Korea, shoulder a greater share of defense costs.

"The United States has important interests in this region, and therefore, because many of those interests are shared with Japan, we have a common interest in strengthening the capabilities of the alliance," Carter told reporters.

Carter said he could not speak for Trump's incoming administration but he knew and respected James Mattis, a retired Marine general, who is Trump's nominee to run the Pentagon.

"I am committed to an orderly handover of responsibilities in the Department of Defense so that my successor can hit the ground running," he said.

"American interests in this region are enduring and our alliance provides many benefits to both our sides."

In a nod to concerns about a rising China, whose aggressive maritime activities in the East and South China Seas have fed territorial rows with several countries in the region, including Japan, Carter said Washington and Tokyo share common interests and values.

"It is very important to stick up for things like freedom of navigation in this region and freedom from coercion, and these are areas that we also have a shared vision," he said.

Carter next heads for India, which has reached a deal with the United States on using each other's military bases for repairs. They have also been cooperating on an Indian aircraft carrier project.