These included convoy attack and screening tactics, inshore patrol, and a large-scale, joint Army-Navy special forces exercise.

"U-553 was sunk a year ago, during a convoy attack."

General Franks said the identities of those killed in the convoy attack or any who might have escaped remained unknown.

Two were killed in a convoy attack by the Taliban.

Missions types include dogfights, escorting or disabling other vessels, convoy attacks, and strikes on capital ships.

Akihiko Saito, a security contractor, was kidnapped after a convoy attack and reported killed on May 28, 2005.

"There is a definite spike in convoy attacks," said the official, who would speak only on condition of anonymity because the information was confidential.

A military statement said one had been killed at an unidentified location in northern Iraq after a convoy attack.

The summary held little new information beyond the previously undisclosed inquiry into the convoy attack on March 2.

The diplomat said the convoy attack on Sunday was unlikely to cause lasting damage to Russian-American ties.