Caroline Kennedy, daughter of former President John F. Kennedy, is expected to be tapped by President Barack Obama as the next ambassador to Japan, according to a person familiar with the selection.

Ms. Kennedy, 55 years old, would succeed Ambassador John V. Roos, who has served in the position since August 2009. Ambassadors serve at the pleasure of the president.

Caroline Kennedy during an interview in New York in March. Associated Press

The White House wouldn't confirm that Ms. Kennedy is in the running for the post.

While briefing reporters on Monday, White House press secretary Jay Carney said in reply to a question about Ms. Kennedy's prospects that he has "no personnel announcements to make."

If she does become the envoy to Japan, Ms. Kennedy would step into the post at a moment when tensions between China and Japan are rising. The two nations have been arguing over control of uninhabited islands in the East China Sea.

One expert on Japan said that Ms. Kennedy would bring to the job undeniable strengths.

"It seems to me that when you want an ambassador, two very important assets are proximity to the president—which she clearly has—and visibility," said Mireya Solis, senior fellow at the Brookings Institution. "There has been a pattern in the past of appointing high-profile people to this post and that [Ms. Kennedy's nomination] would fit into the pattern. This is a complicated region, but she has those two very important assets."

Ms. Kennedy, together with her late uncle, Sen. Edward Kennedy, gave Mr. Obama a coveted endorsement in the 2008 Democratic primary fight. With both Hillary Clinton and Mr. Obama competing for the Kennedy family endorsement, Ms. Kennedy and her uncle chose to back Mr. Obama's insurgent candidacy.

In an opinion column in the New York Times in January 2008, Ms. Kennedy wrote: "Over the years, I've been deeply moved by the people who've told me they wished they could feel inspired and hopeful about America the way people did when my father was president. This sense is even more profound today. That is why I am supporting a presidential candidate in the Democratic primaries, Barack Obama."

The White House hasn't disclosed when it would announce Mr. Obama's slate of new ambassadors. But the White House has made calls to various candidates saying the president intends to nominate them pending a background check, according to another person familiar with the selection process. A message left with the office of Ms. Kennedy's husband, Edwin Schlossberg, was forwarded to Ms. Kennedy's office. It wasn't returned.

Japan's government hasn't received any formal notice of an appointment, chief spokesman Yoshihide Suga said early Tuesday in a regular press briefing. "However, President Kennedy is a very familiar name in Japan, and we'll be watching closely for the final decision," he added.

The White House is still trying to match candidates with countries where they might serve, and it is possible Ms. Kennedy could be chosen for a different country. One other possibility is Canada.

—Toko Sekiguchi in Tokyo contributed to this article

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