Donald Trump plans to appoint William Hagerty, a key member in his transition team, as ambassador to Japan, an aide inside the U.S. president-elect's inner circle said Wednesday.

Hagerty's purported appointment, a move that appears to show Trump is placing weight on U.S. ties with Tokyo, has already been conveyed to the Japanese government, the aide said.

Hagerty is in charge of political appointees for Cabinet and other senior posts in the Trump administration, which takes office Jan. 20.