The U.S. battleship fleet has received a vote of confidence from President Bush.

Bush, a World War II Navy veteran, said Thursday the Navy would make a full investigation of the accident to find out what happened but added he would not consider putting the Iowa or its three mammoth, heavily armored sister ships - the New Jersey, Missouri and Wisconsin - back in "mothballs."Battleships have been a source of some debate in military circles since World War II, with some experts arguing that the huge fuel-guzzling craft had become outmoded sitting ducks in the age of swift, long-range missiles and supersonic aircraft.

The U.S. fleet was brought out of storage and refurbished at great cost as part of former President Reagan's buildup, despite some opposition, and it seemed the disastrous Iowa accident might revive calls for their retirement.

Under questioning by reporters Thursday, Bush made it clear he thinks it premature to call the great ships obsolete.

"I wouldn't jump to the conclusion that, because that kind of powder is put into these turrets in that way, that that makes a useful platform obsolete," he said. "I'm not going to go that far."

Capt. Larry Seaquist, the former commander of the Iowa, told reporters at a Pentagon briefing that the cause of the accident was unknown, but "it seems from the reports that the powders exploded."

The black gunpowder was made during the Korean war and kept in storage after the Iowa and other U.S. battleships were decommissioned, then remixed when the ships were activated by Reagan. Seaquist said the powder was very stable.

But the turrets are so well armored that they provide what military experts call a "steel tomb" if something goes wrong.

Bush, then vice president, commissioned the Iowa in 1984.