WASHINGTON -- The commander of the USS John S. McCain when it collided with a commercial tanker last year in the Straits of Singapore pleaded guilty Friday to dereliction of duty and acknowledged his role in the deaths of 10 sailors.

Cmdr. Alfredo Sanchez appeared somber and tearful during a special court-martial at the Washington Navy Yard for the criminal charge under the Uniform Code of Military Justice. Sanchez pleaded guilty as part of an agreement reached earlier this year and has yet to be sentenced, but could face a letter of reprimand and forfeiture of a portion of his pay for three months.

Sanchez, who has spent more than 20 years in the service, said he will retire as part of the agreement.

"I failed to set" the appropriate crew needed for the crash, Sanchez said. "I should have directed more rigorous training."

A day earlier, Chief Petty Officer Jeffery D. Butler, who was charged with training and use of a navigational system on the McCain, pleaded guilty to dereliction of duty and also acknowledged his role in the deaths.

Friday's hearing, which was attended by several relatives of the sailors who died Aug. 21, is one of a series of courts-martial resulting from the McCain collision. For about two hours, relatives read searing and emotional victim impact statements.

"This is a tragedy that should have never happened," said Karen Doyon, mother of Petty Officer 3rd Class Dustin Doyon, 26, of Connecticut.

In January, Navy officials said Sanchez had been charged with negligent homicide, dereliction of duty and hazarding a vessel.

A charge sheet released Wednesday said Sanchez was facing "a dereliction in the performance of duties through neglect resulting in death." The charge sheet went on to say that Sanchez knew of his duties as commanding officer and was derelict in the performance of those duties.

"He negligently failed to ensure the safe navigation of the said vessel," the charge sheet said, "as it was his duty to do as Commanding Officer to ensure a proper watch was set for transiting a high-density contact environment; take proper action and control of the vessel during system casualty; follow operational Standing Orders during a conceived system casualty, and that such dereliction of duty contributing to the death" of the 10 sailors.

The new details didn't mention the homicide charge or hazarding a vessel. The Navy didn't respond Thursday when asked why the charges details had changed.