North Atlantic Treaty Org. (NATO)
 

If it is determined that this attack was directed from abroad against the United States, it shall be regarded as an action covered by Article 5 of the Washington Treaty," stated NATO Secretary General, Lord Robertson, after a meeting of the North Atlantic Council on the evening of 12 September.

Article 5 of the Washingon Treaty stipulates that an armed attack against a member shall be considered as an attack against all. Lord Robertson will now officially inform the UN Secretary-General Kofi Annan, that the North Atlantic Council has agreed this statement.
http://www.nato.int/

Members of Nato & EAPC
http://www.nato.int/multi/map.htm

my6

Sweet.