The crash occurred at a forward supply and refueling point in southern Iraq. According to the spokesman, the incident was not a result of enemy fire, but the cause remained unclear.
Neither Central Command in Qatar nor the Pentagon would confirm the exact location of the accident.
Four people were believed to be aboard the helicopter, which had been taking off on a support mission.
In Washington, a Pentagon official speculated the crash may have been caused by bad weather.
“Early indications are that on take-off, the helicopter crashed,” the Pentagon official said.
The incident is the third reported accident involving helicopters since the war opened 10 days ago.
Eight British royal commandos and four U.S. Marines were killed March 20 when a U.S. Marine helicopter crashed south of the Iraqi border in Kuwait, Pentagon officials report. The crew of 12 became the first coalition casualties of the war with Iraq.
The next day, two British helicopters collided and crashed over the Persian Gulf on Friday, killing seven crewmembers, including a U.S. Navy officer.