A new audiotape said to be from the al-Qaeda leader's deputy Ayman al-Zawahri taunts the US over its efforts to stabilise Afghanistan.
Ayman al-Zawahri (r) is Bin Laden's right-hand man
The six-minute recording was broadcast by the Arabic TV news channel Al-Jazeera on Friday.
The tape says US forces have failed in Afghanistan and warns that al-Qaeda is pursuing Americans "everywhere".
The tape was made, the speaker said, to coincide with the second anniversary of the Tora Bora offensive in Afghanistan.
Earlier this month, the BBC received a videotape showing Taleban forces regrouping.
It showed Taleban fighters roaming freely in southern Afghanistan and preparing home-made bombs.
Mr Zawahri repeatedly urged US citizens to oppose the policies of US President George W Bush.
"How can we excuse you after all the warnings that we gave you? You reap what you sow," the message on Friday said.
The speaker said America had "failed militarily, despite the huge arsenal of weapons it possesses and the rivers of dollars it poured into Afghanistan".
"Two years after Tora Bora [the battle], we are still, as we had been, with the blessings of God, pursuing the Americans and their allies everywhere and, in fact, in their own backyard," he added.
The speaker threatened Arab countries that had provided "bases and help" to US forces to fight Muslims, saying they
should be ready for "judgment day".
Qatar, Kuwait and Bahrain provided bases and logistics for the US to invade Iraq.
About 12,000 US-led troops remain in Afghanistan following the American invasion of the country in 2001, which defeated the hardline Taleban regime.
Taleban and al-Qaeda militants are still active in the mountainous south-east of the country.
Egyptian-born Ayman al-Zawahri joined up with Osama Bin Laden in 1998.
He was indicted in New York two years ago in connection with the 1998 embassy bombings in Kenya and Tanzania.