U.S. Military officials say the Department of Defense is reviewing its policies on the use of social networking Web sites such as Twitter and Facebook.

Deputy Defense Secretary William Lynn has ordered the department-wide review saying these Web sites could compromise security.

Lynn said while social networking Internet sites are useful to the military for recruiting purposes, public relations, and sharing information with military families, they present risks that must be better understood.

Lynn said the Pentagon's new policy on the sites will be developed by the end of September.

Although there is currently not a department-wide ban on social networking, the U.S. Marine Corps, which has long prohibited its personnel from using the Web sites on work computers, issued a formal ban on them on Monday.

Marine Corps officials say the ban does not affect Marines using the social networks on their personal computers.  Officials also say Marines whose assignments require use of the Web sites will be granted access.  

Some information for this report was provided by AFP, AP and Reuters.