As a sign of support for the United States, NATO invoked its mutual defence clause for the first time in its 52-year history. This has opened the way for a possible collective military response to the shattering attacks. The German Chancellor Gerhard Schröder made clear that Germany would stand at the side of the US in the fight against terrorism.

NATO's defence clause commits each of the 19 member nations to take "such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area."

Germany, however, requires parliamentary approval each time it deploys troops outside the country. Chancellor Schröder told a news conference it was too early to speculate about Germany's involvement in any military action, but said he would keep in close touch with NATO partners.

"We have yet to decide on the content and extent of any German involvement...we will continue to work very closely with our NATO partners, particularly our friends in the United States," Schröder said.