The West's moves to isolate the new Hamas-led Palestinian government prove it is at war with Islam, a tape attributed to Osama Bin Laden declares.
If the tape is genuine, it is Bin Laden's first message since January
The tape also described the situation in Iraq and Sudan's troubled Darfur region as further evidence that a "Zionist-crusader war" was being waged.
The recording was broadcast by Arab satellite TV al-Jazeera on Sunday.
The White House said US intelligence believed the tape was authentic.
If so, it is the first message from Bin Laden since January 2006, when he threatened more attacks on the US.
The speaker on the tape said that along with their governments, the people of the West bear responsibility for what he called a "Zionist-crusader war against Islam".
"The war is a responsibility shared between the people and the governments. The war goes on and the people are renewing their allegiance to its rulers and masters," he said.
"They send their sons to armies to fight us and they continue their financial and moral support while our countries are burned and our houses are bombed and our people are killed."
He said that the decision by some Western powers to cut funding to the Palestinian government since the militant group Hamas won elections there was further proof of this anti-Islamic campaign.
White House spokesman Scott McClellan said the tape had been assessed as authentic by intelligence agencies.
"The al-Qaeda leadership is on the run and under a lot of pressure," he told reporters.
"We are continuing to take the fight to the enemy abroad and making it difficult for them to plan and plot against Americans."
But the US ambassador in Iraq, Zalmay Khalilzad, warned that Bin Laden still posed a threat.
"I believe we need to take him seriously," he said in an interview with CNN, adding that Bin Laden wanted to show he was "still a player".
The Hamas government moved quickly to distance itself from the tape, saying it was keen to maintain good relations with the West.
Hunt in borderlands
The speaker also criticised Western involvement in the troubled Darfur region of Sudan, saying it was part of the "crusades against Islam" and called for militants to journey there to join the fight.
"I call on mujahideen and their supporters, especially in Sudan and the Arab peninsula, to prepare for long war again the crusader plunderers in Western Sudan," the voice said. "Our goal is not defending the Khartoum government but to defend Islam, its land and its people."
Bin Laden was based in Sudan until he was expelled following US pressure on Khartoum.
He then moved to Afghanistan and is now believed to be hiding in the mountains on the Pakistani side of their shared border.
But successive operations involving coalition troops inside Afghanistan and Pakistani forces along their side of the border have so far failed to track down the al-Qaeda leader.