A key economic adviser to Prime Minister Shinzo Abe who has been a strong advocate of monetary stimulus will become Japan's ambassador to Switzerland, according to a notice issued by the Prime Minister's Office on Friday.

Etsuro Honda, 61, a former Finance Ministry bureaucrat who has known Abe for decades, will combine his new post in Switzerland with his existing advisory duties, the top government spokesman said.

"Mr. Honda will continue to provide advice to the prime minister as he has up until now, combining his roles," Chief Cabinet Secretary Yoshihide Suga told reporters, when asked whether Honda's absence would allow the Finance Ministry to exercise more influence over the premier.