Some of the Italian forces may see ground action
Defence Minister Antonio Martino told parliament the force would include naval, air and ground units.
Some might be involved in combat operations, he said, but the majority would be involved in logistical and defensive tasks.
The announcement came as the German cabinet approved Chancellor Gerhard Schroeder's pledge on Thursday to provide a force of nearly 4,000 troops at the request of the US.
Mr Schroeder stressed that German troops would not be involved in ground combat.
Combat mission
"The army will provide a 1,000-strong contingent which could be used in a successive stage of the mission with armed escort tasks and helping humanitarian organisations," Mr Martino said.
Mr Martino said the Italian force would be placed under the direct command of the US military.
Four attack helicopters would be provided for "combat operations", Mr Martino said.
The Italian aircraft carrier Garibaldi will join the force, backed up by one or two frigates operating in the Gulf.
Harrier jump jets, transport and fuel supply planes also committed. Between six and eight Tornado jets will carry out reconnaissance missions and aerial defence.
"No-one should delude themselves into thinking that the war against terrorism will be brief, painless and limited. But we must be aware that this is a struggle of civilisation against barbarity," Mr Martino said.
"We cannot underestimate the risk that this mission brings," he added.
"The possible risks to the coalition include terrorist actions, both in the areas where the military is deployed as well as on respective national territories."
Europe's commitment
The commitment of forces means Italy joins France, the UK, Germany and Turkey in mobilising specific support from Europe for the US-led war.
President Jacques Chirac said France already had 2,000 troops involved in the campaign and Prime Minister Lionel Jospin said it was ready to increase that commitment.
On a visit to the United States on Tuesday, Mr Chirac stressed the need for a broad approach to the war on terrorism, with a particular focus on building a viable post-Taleban regime.
Germany's contingent will include special forces, medical services, air transport and naval forces as well as experts in nuclear, biological and chemical weaponry.
The lower house of parliament, the Bundestag, is due to vote on the deployment on Thursday.