The Navy hopes a high tide due to reach Hawaii early Saturday will enable it to refloat a 9,600-ton warship that ran aground about a half mile off seaside Honolulu International Airport.

An initial effort by Navy tugs early Friday to free the guided missile cruiser USS Port Royal was unsuccessful. The $1 billion ship ran aground Thursday night while carrying guests that included a rear admiral.

"We're certainly working on bringing to bear the resources we have to move her off the current position. We're still putting that plan together," said Capt. W. Scott Gureck, a spokesman for U.S. Pacific Fleet. "Obviously, the high tide gives us an opportunity to do that."

Divers and the salvage ship USS Salvor would try to tow the 567-foot vessel, the Navy said.

The cause of the grounding on the sandy bottom and the extent of damage to the vessel were under investigation.

"I'm not going to speculate on what happened," Gureck said.

The Port Royal left Pearl Harbor on Thursday for sea trials after being dry-docked for routine maintenance. The ship ran aground while shore-based officials were being transferred to shore by small boat, the Navy said.

An oil recovery vessel, the Clean Islands, was positioned behind the warship as a precaution as the U.S. Coast Guard monitored the situation.

"We know that there is no oil spill at this point, and we're confident the Navy is doing everything it can," Coast Guard Lt. John Titchen said.

Commissioned in 1994, the Port Royal has a crew of about 360. The crew stayed aboard the ship, along with Navy officials such as Rear Adm. Dixon R. Smith, commander Navy Region Hawaii and Naval Surface Group Middle Pacific.