The U.S. Army apologized Wednesday for sending 7,000 letters to family members of soldiers killed in Iraq and Afghanistan -- and addressing the letters to "John Doe."

Army Chief of Staff Gen. George W. Casey Jr. is sending a personal letter of apology to all the families who received the letters.

The 7,000 original letters were sent late last month by a contractor to inform survivors about private organizations that offer gifts, programs and other assistance to families of soldiers who were killed in the War on Terror.

Army spokesman Paul Boyce blamed the mistake on a faulty "mail merge" function within a high-speed printer the Army uses to send out mass mailings.

The letters were sent from the U.S. Army Human Resources Command's Casualty and Mortuary Affairs Center in Alexandria, Va, which issued a formal apology on Wednesday.

"There are no words to adequately apologize for this mistake or for the hurt it may have caused," Brig. Gen. Reuben D. Jones, the Army Adjutant General, said in a statement to be posted on the human resources Web site.

"It is important the original intent of the letter is not lost. The organizations mentioned are dedicated to honoring loved ones and recognizing their sacrifice and commitment."

According to the Washington Post, 4,829 U.S. service members have died in Iraq and Afghanistan since 2001 -- 4,204 in Operation Iraqi Freedom and 625 in Operation Enduring Freedom.

FOX News Justin Fishel and The Associated Press contributed to this report.