AVIANO, Italy (Reuters) - The United States on Thursday acknowledged that the crew of a Marine Corps jet was to blame for a cablecar tragedy in Italy's Dolomites mountains last month in which 20 people died. "It was an aircrew error. The crew flew lower and faster than authorised whenever...there was a valley," Major General Michael DeLong told a news conference at the U.S. airbase in Aviano. DeLong, who was still addressing reporters at the Aviano news conference, headed the Marines' inquiry into the accident on February 3. The U.S. surveillance aircraft, which was on a training mission, sheared cablecar wires in the ski resort of Cermis and sent a cabin plunging into an icy mountainside. All passengers, including a 12-year--old boy, died on impact, crushed in the mangled wreckage of the cablecar. A U.S. official at the Pentagon told Reuters on Wednesday that the inquiry found the accident could have been avoided and recommended disciplinary action against the four-man crew. La Repubblica newspaper said on Thursday it had obtained a copy of the U.S. military report. "The crew piloted the plane in an aggressive way, exceeding speed limits and flying well below the set limit of 1,000 feet (300 metres) in two of the six stages of the flight plan," it quoted the report as saying.