President George W Bush said the Pentagon is in hot pursuit of terrorists behind the September 11th attacks.
He admitted US special forces had been operating inside Afghanistan.
"Make no mistake about it, we're in hot pursuit of terrorists," the president told reporters.
He added very little detail, but added that he understood it is "very hard to fight a guerrilla war with conventional forces".
At another point, he said "there may or may not be a conventional component" to the war on terrorism.
Small teams of US commandos backed by Blackhawk helicopters reportedly have been searching for bin Laden in caves and underground bunkers in southwestern Afghanistan for two weeks. British special forces were also reported to be participating in the operations.