The U.S. Navy may have to delay raising a Japanese high school fisheries training ship sunk by a U.S. submarine until after mid-September, a navy captain indicated Friday.

"We have incurred some additional time frame in the fact that we have to do some redredging," Capt. Bert Marsh told a news conference.

"That shouldn't be a major delay, but to try to get too specific, I really can't do that at this time," said Marsh, the navy's director of ocean engineering and supervisor of salvage.

Marsh has been overseeing operations to lift the Ehime Maru from its current depth of about 600 meters to a shallow shoal. There, divers will attempt to retrieve the remains and personal effects of the nine missing people, some of whom are believed to be still entombed within the vessel. But for more than two weeks, technicians have been unable to start rigging the ship because they have been unable to position two steel lifting plates under it.