The Pentagon has ordered an increase in the force protection level at military bases in the United States before the 10th anniversary of the Sept. 11, 2001 terrorist attacks, authorities said Wednesday.

Pentagon Spokesman George Little said Defense Secretary Leon Panetta has approved a request by U.S. Northern Command to raise the Force Protection Condition (FPCON) through Sunday.

The FPCON, a system overseen by the Pentagon, describes the amount of measures needed to be taken by security agencies in response to various levels of terrorist threats against military facilities.

Little stressed that the move was taken not due to a specific terror threat, but as a "prudent and precautionary measure." He noted that terrorists have shown interests in anniversaries and documents recovered from the compound in Abbottabad, Pakistan, where Osama bin Laden was killed, also mentioned the Sept. 11 anniversary.

White House Press Secretary Jay Carney said Wednesday that the administration would be "ever vigilant" on Sunday's anniversary. Earlier this month, Secretary of Homeland Security Janet Napolitano said the U.S. remains at "a heightened state of vigilance" and security measures are in place to detect and prevent plots against the United States should they emerge.

On Sept.11, 2001, terrorists hijacked two of the passenger planes and crashed them into the twin towers of the World Trade Center in New York City, killing nearly 3,000 innocent civilians.