U.S. Defense Secretary James Mattis wrapped up his four-day trip to Asia on Saturday, reassuring Japan and South Korea that America is committed to the security of the Asia-Pacific region despite fears of abandonment stoked by President Donald Trump.

If Tokyo's biggest goals were to have Washington reaffirm the importance of the Japan-U.S. alliance and to have Mattis confirm that the U.S. is committed to the defense of the disputed Senkaku Islands in the East China Sea, then it accomplished its mission, experts said. At least for the moment.

"I think the Abe administration is now relieved," said Mikio Haruna, a noted journalist who specializes in diplomacy and is a visiting professor at Waseda University in Tokyo. "Trump has said many things that contradict the mutual understanding between Japan and the U.S., but Mattis has made it clear that Trump's position (on the alliance) is not so different from Obama's."