President Barack Obama is leaning towards picking Caroline Kennedy to be the next US ambassador to Japan.

The 55-year-old daughter of former president John F Kennedy would be the first female US ambassador to Japan.

She was one of the earliest backers of Mr Obama in his first presidential campaign in 2008.

Her endorsement was significant in helping him defeat Hillary Clinton in the Democratic presidential primary that year.

The author and lawyer serves on the board of several non-profit organisations.

She would replace the current ambassador, John Roos.

He is the former chief executive of Silicon Valley-based law firm Wilson Sonsini Goodrich & Rosati.

White House spokesperson Jay Carney declined to comment on whether Mr Obama had settled on Ms Kennedy to represent the US in Japan, one of America's top Asian allies.

"I have no personnel announcements to make," he said.

The Japan ambassadorship is an important diplomatic posting for the US at a time when it is keeping a careful eye on China as well as North Korea.