An American soldier was arrested on Thursday night at Fort Lewis, Washington, on charges of trying to pass information about military capabilities to Al Qaeda

Spc Ryan G Anderson, 26, is a National Guard soldier, military officials told CNN. He was arrested after an internal sting operation. Fort Lewis is near Tacoma.

"He will be charged with aiding the enemy by wrongfully attempting to communicate and give intelligence to the al Qaeda terrorist network," base spokesman Lt Col Stephen Barger told CNN.

The investigation will be carried out by the army, the Federal Bureau of Investigation and the Justice Department.

Pentagon officials said Anderson allegedly offered to pass information to Al Qaeda agents through an Internet chat room. But sources told CNN that Anderson did not actually make contact with Al Qaeda members.

Anderson is part of the 303rd Armour Battalion of the 81st Armour Brigade. He was first noticed by law enforcement personnel monitoring the chat room.

The sting operation involved passing sensitive information about capabilities and vulnerabilities of armoured Humvees and tanks, officials said.

The brigade is preparing to deploy for final training in California before it departs for a tour in Iraq.

Anderson converted to Islam five years ago, according to Anderson's wife quoted by Everett Herald newspaper.

Agencies