A senior Pentagon official says the US will launch sustained military strikes against those behind the attacks on New York and Washington.
Deputy Defence Secretary Mr Paul Wolfowitz said the strikes would also be aimed at their support systems.
He said the military retaliation would continue until the roots of terrorism were destroyed.
At a news conference he said: "One has to say it's not just simply a matter of capturing people and holding them accountable, but removing the sanctuaries, removing the support systems, ending states who sponsor terrorism".
Other Defence Department officials, speaking on condition of anonymity, said the administration was considering options that included the use of air, sea and land forces over a lengthy period.
They said it was clear the administration would go well beyond the limited strikes of recent years against Iraq, Afghanistan and Sudan.
Navy Secretary Mr Gordon England said: "This is not going to be a short programme."
