Nato approved requests from the United States for specific military contributions in the campaign against terrorism, Secretary–general Lord Robertson said.
The move by the 18 NATO countries came after Washington offered evidence of Osama bin Laden's involvement in the New York and Washington attacks.
"Today's decision clearly demonstrates the allies' resolve to combat terrorism," Lord Robertson said. He added the commitments were "clearly not time–limited."
In Rome, Italy's Foreign Minister Renato Ruggiero said the US requests to Nato included access to alliance members' ports, airspace and airports and the ordering up of naval forces in the Mediterranean.
"The alliance is ready to deploy elements of its standing naval forces," Robertson said.
Mr Ruggiero also said the United States had asked that Nato countries made available radar aircraft as well as provide financial aid to Pakistan and other countries involved in the campaign.
Diplomatic sources at Alliance headquarters have said the aid requested was essentially a compilation of the kinds of support the United States already has obtained from member states on a bilateral basis.
France, for example, has agreed to American requests to open its airspace and has offered naval and logistics support in the Indian Ocean.
Germany said the US request included cooperation on intelligence, protection of US installations in Nato countries, unlimited overflight rights and air space surveillance. The chancellor said he told the German representative to Nato to cooperate in helping the United States with its needs.
On Tuesday, the allies formally invoked Article 5 of the Nato constitution, which says an attack against one member is an attack against all.
The decision on the request for assistance from the United States was taken by the so–called silent procedure, by which the member states agree if they do not raise objections by a certain deadline.Reuse content