U.S. Vice President Mike Pence will visit Japan and Indonesia as part of an Asian tour next month, sources said on Monday, amid concerns the Trump administration is rolling back Barack Obama's "pivot to Asia."

U.S. President Donald Trump has already withdrawn from the Trans-Pacific Partnership (TPP) trade agreement, which was seen as an economic pillar of the strategy.

The tour will include South Korea and Australia, the Nikkei Asian Review reported, with North Korea's missile and nuclear programs and South Korea's political crisis likely topics for discussion.