US President Barack Obama said he would name Caroline Kennedy, daughter of the late President John F Kennedy, as ambassador to Japan.
Ms Kennedy, who trained as a lawyer, is president of the John F Kennedy Library Foundation and chairs an advisory committee at the Institute of Politics at Harvard University.
Active in Democratic politics, the 55-year-old was an early and prominent supporter of Mr Obama's in his initial quest for the presidency in 2008.
Her appointment is subject to Senate confirmation.
Ms Kennedy's endorsement, along with that of her uncle, the late Senator Edward Kennedy, gave Mr Obama the stamp of approval of one the most important names in Democratic politics and provided an enormous boost to his candidacy.
Japan is a particularly close and important ally of the United States, and past US ambassadors have been well-known political figures, including former Vice President Walter Mondale.
The previous US ambassador was California lawyer John Roos.
