The U.S. Department of Defense has blocked access to some social networking sites on its computers, saying use of the sites could clog the military's networks, a spokeswoman said Tuesday.

The restrictions, which went into effect Monday, had been considered for some time, said Lt. Col. Randi Steffy, a spokeswoman for the U.S. Strategic Command, which is overseeing the task force that designed the restrictions.

"The consideration here is a bandwidth issue. The .mil domain needs to be preserved for the operational requirements, and it was looked at that many of these sites with the video usage and that sort of thing essentially clog up the systems so they decided to put in restrictions," Steffy said. "Security was a small consideration but it really was a bandwidth/network management issue."

Although Steffy declined to name the sites that were restricted, published reports said they include YouTube, MySpace and 11 other Web sites where soldiers post photos, videos and audio recordings to share with family and friends.

However, soldiers will still be able to access these sites from nonmilitary computers, such as those found in Internet cafes.

Earlier this month, the Army issued a regulation barring soldiers from blogging, taking part in online discussion groups or sending personal e-mails unless they clear the content beforehand with a superior officer, according to a document obtained by Wired Magazine.

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