President Barack Obama on Wednesday nominated Caroline Kennedy to become US ambassador to Japan, in the biggest foray into public service for John F. Kennedy's sole surviving child.

The former first daughter, who long resisted running for public office, if confirmed will enter a limelight not seen since her childhood as she becomes the face of the United States in one of its closest allies.

Japan hailed the announcement, saying that Kennedy -- a crucial early supporter of Obama's presidential bid -- enjoyed the "deep confidence" of the president.

Japan "highly appreciates her nomination as reflecting the great importance the Obama administration attaches to the Japan-US alliance," a foreign ministry statement said.

Obama offered an understated rollout to the long rumored nomination, with the White House issuing a statement calling Kennedy and unrelated nominees "fine public servants."

By tapping the 55-year-old known around the world as a girl in the White House, Obama was returning to a tradition of making Tokyo one of the most high-profile US diplomatic jobs.

Previous US ambassadors have included former vice president Walter Mondale, former speaker of the House Tom Foley and former Senate majority leader Howard Baker.

By contrast, Obama's first-term ambassador John Roos -- known primarily as a campaign fund-raiser -- was seen by some Japanese commentators as a sign of a lower US priority on the country.

Roos, however, was later praised for handling the round-the-clock US response to the March 2011 tsunami disaster.

Weston Konishi, director of Asia-Pacific studies at the Institute for Foreign Policy Analysis, said that Obama likely picked Kennedy knowing that Japan wanted a prominent ambassador.

"Caroline Kennedy certainly fits that bill, coming from a legendary American family. I am sure she will be a very popular figure in Japan," Konishi said.

But despite the official praise for Kennedy, Konishi said that Japanese policymakers may have preferred a figure with prior foreign policy experience in light of recent tensions between Japan and its neighbors, especially China.

"I think there is less excitement about the nomination at the elite level," he said.

Kennedy is not known for any direct connection to Japan, although she visited in 1986 during her honeymoon with her husband Edwin Schlossberg.

Her father was seriously wounded by a Japanese destroyer during World War II. But Kennedy was perhaps best remembered in Tokyo for naming as ambassador Edwin Reischauer, a Japan scholar credited with building the post-war alliance.

Caroline Kennedy needs to be confirmed by the Senate, but she has no open critics and the body is led by the Democratic Party which reveres her father.

Kennedy was five days short of her six birthday when her father was assassinated in 1963. She suffered further tragedies when her mother, Jacqueline Kennedy Onassis, died in 1994 and her brother, John F. Kennedy Jr., was killed in a plane crash in 1999.

The family's sole survivor has supported the Kennedy brand of progressive politics but mostly shunned the spotlight other than writing books on civil liberties.

But Kennedy offered a major boost to Obama's presidential campaign in 2008 when she threw her family's prestige behind the then senator instead of perceived Democratic front-runner Hillary Clinton.

In an opinion piece for The New York Times, Kennedy wrote that the first-term senator could become "a president like my father."

If confirmed, Kennedy would be the first woman to take up the post, a feat sure to be noticed in a country that has historically ranked lower than other wealthy nations on women's empowerment.

Kennedy would take over at a time of friction between Japan and a rising China over a territorial row, although she can expect to see relative stability in US-Japan relations.

Conservative Prime Minister Shinzo Abe's coalition won a comfortable victory in upper house elections Sunday, ending an era of divided parliaments that led to the rapid downfall of six premiers since 2006.

Obama faced hiccups in his relationship with Japan during his first year when left-leaning prime minister Yukio Hatoyama took office and called for a more "equal" relationship with Washington.