The yen may strengthen to a postwar high against the dollar because of the weakness of the U.S. economy, said former Finance Ministry official Eisuke Sakakibara, known as "Mr. Yen."
"The yen may appreciate further, beyond 75," Sakakibara said in an interview Monday. "I would expect the U.S. economy to be fairly weak for a long period of time."
The yen declined Monday after Finance Minister Yoshihiko Noda warned that he's ready to intervene again to stem yen gains that pose a risk to exports. The yen is approaching its all-time high of 76.25, underscoring the difficulty that authorities are having in halting its advance.
"Intervention, to be effective, needs to be persistent and continuous and needs to have the understanding" of other authorities, said Sakakibara.
"Multilateral intervention does work, but I don't think at the moment the U.S. is willing to intervene," he said. "It will be very difficult to have a coordinated intervention."
The yen has appreciated 5 percent in the past three months.