Japan should take a more "proactive" diplomatic role as part of efforts to strengthen relations with the United States in the post-President George W. Bush era, according to a seasoned U.S. expert on Japan.

"The first thing, I think, is that Japan needs to be proactive and this is the time to prepare," said Kent Calder, director of the Reischauer Center for East Asian Studies at Johns Hopkins University's School of Advanced International Studies.

He said in a recent interview that so-called Japan-passing is probably happening in the U.S. — an English phrase coined in Japan that means passing Japan by as a result of a decline in U.S. interest in the country.

"Japan is hugely important for the United States. It's hugely important for the world. . . . And yet, strangely enough, we are not hearing a lot about it," he said.