"She is known to be very close to President Obama. As U.S. ambassador, one of the most crucial questions is if or how he or she can communicate a variety of issues with the president. For that role I would give her a big welcome," Suga said.
The 55-year-old Kennedy was instrumental in helping put Obama in the White House, where her father, President John F. Kennedy, served until his assassination 50 years ago.
If confirmed as ambassador to Japan, one of the United States' most important trading and military partners, she would be the first woman in the post. She would replace John Roos, a wealthy former Silicon Valley lawyer and a top Obama campaign fundraiser.
Obama announced the nomination Wednesday, offering the most famous living member of a prominent American family a new role of service to the country.
Many U.S. envoys to Japan have been big political names, such as former Vice President Walter Mondale and the late senator Mike Mansfield.
In a country that likes prestige and famous brands, though, the family name Kennedy would be certainly well received.
"Many Japanese people feel close to the late President Kennedy," Suga said, adding that Japan's government is willing to support her.
Kennedy lacks any obvious ties to Japan, a key ally in dealing with North Korea's nuclear ambitions, and some experts have expressed concern that she might lack the capacity to handle thorny issues in the U.S.-Japan relationship such as trade talks, tensions between Japan and China, and frictions over U.S. military personnel based in Japan.
Suga shrugged such issues aside, but some Japanese media — most of which covered the late breaking news briefly in their Thursday evening editions — noted that Kennedy's potential as a diplomat is untested.
"Glorious Family, but Abilities Unknown," said a front-page headline in the newspaper Mainichi Shimbun.
Some Japanese have expressed hope that Kennedy might be a good role model for Japanese women aspiring to leadership positions in a society traditionally dominated by older men. Prime Minister Shinzo Abe has said he favors reforms aimed at promoting a stronger role for women in business, such as wider provision of child care and longer leaves for new parents.
Kennedy helped propel Obama to the 2008 Democratic presidential nomination in a celebrated endorsement over Hillary Rodham Clinton, the only time she's endorsed a presidential candidate other than her uncle Ted Kennedy in 1980.
She earned a bachelor's degree from Harvard University and a law degree from Columbia University. She married exhibit designer Edwin Schlossberg and had three children.