The midmorning accident between the amphibious assault ship USS Essex and the oiler USNS Yukon occurred about 120 miles off the coast of Southern California as the Essex was approaching the Yukon to get in position to be refueled, said Cmdr. Charlie Brown, a spokesman for the 3rd Fleet.
Navy officials said there apparently was a steering malfunction on the Essex, which was carrying 982 crew members on its way to San Diego for scheduled maintenance. It had spent the past 12 years based in Sasebo, Japan, as command ship for the Navy's Expeditionary Strike Group 7.
Both ships were able to continue toward San Diego despite the damage, which did not compromise their fuel tanks or systems, Navy officials said.
The Yukon arrived at the Navy base in San Diego after 3 p.m. Wednesday with its crew of 78. All but four are civilian mariners.
The Essex was keeping to its planned arrival time of 9 a.m. Thursday.
Brown said the degree of the damage was still being assessed. He said he couldn't say how fast the ships were moving at the time of the crash because the Navy is still investigating the cause of the collision.
The standard speed for ships lining up to refuel at sea is about 13 knots, Brown said. No lines or hoses had been connected yet since the two vessels were just approaching each other.
The ships' speed, about 15 mph, is not very fast, so they likely just bounced off each other, said maritime safety consultant J.W. Allen.
Even so, he said, with massive ships, it can be "a pretty hard bump that can bend metal" and cause dents. The Essex resembles a small aircraft carrier, while the Yukon is 677 feet long.
Navy ships routinely refuel at sea while under way.
"They were probably so close there was no time to respond when the steering went out," said Allen, who served 30 years in the Coast Guard.
The Yukon, which was launched in 1993, has been involved in at least two previous collisions, including on Feb. 27, 2000, when it collided with a 135-foot civilian cargo ship while trying to enter Dubai's Jebel Ali port in the United Arab Emirates. The Yukon sustained minor damage.
Less than five months later, it was hit by the USS Denver during refueling off the coast of Hawaii. Both ships sustained heavy damage.
Navy officials said it was the Essex's first collision.
A helicopter based on the Essex crashed off Hawaii in 1995, injuring four. In 1996, another of its helicopters crashed into the Indian Ocean off the coast of Africa where it was helping in the departure of U.N. peacekeepers from Somalia.
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Associated Press writers Andrew Dalton and John Antczak in Los Angeles contributed to this report.
