US intelligence agencies believe the latest tape released by Al Qaeda leader Osama bin Laden is authentic, the White House says.
Al Jazeera television has aired an audiotape that is attributed to the fugitive leader.
In it, he urges his followers to prepare for a long war against Western would-be occupiers in Sudan's Darfur region.
The speaker also says the West's shunning of the Hamas Palestinian Government shows it is waging a "Crusader-Zionist war" on Muslims.
"We just heard from the intelligence community that they believe it's authentic," White House spokesman Scott McClellan said.
Mr McClellan says Al Qaeda's leaders are on the run and under pressure.
"We are continuing to take the fight to the enemy abroad and making it difficult for them to plan and plot against Americans," he said.
"We continue to take all terrorist threats seriously and that is why we are acting on all fronts doing everything within our power to prevail in the war on terrorism."
Al Jazeera has declined to reveal how it obtained the tape and has not said if it is dated.
However, the tape have to have been recorded after March 14 because of bin Laden's reference to an Israeli raid on a West Bank prison on that date.
Hamas
Hamas has moved quickly to distanced itself from the comments, in which bin Laden also refers to the cutting of funds by Western governments to the Palestinian Government.
Hamas spokesman Sami Abu Zuhri says his group's ideology is completely different to that of bin Laden's.
But he acknowledges that the international funding freeze on Hamas is creating tension in the Arabic and Islamic world.
Bin Laden has been on the run since the US campaign to oust Afghanistan's Taliban government in 2001 after the September 11 attacks.
He and his right-hand man, Ayman al-Zawahri, are believed to be hiding in a mountainous area on the border between Pakistan and Afghanistan.
- ABC/Reuters
FBI photo of Osama Bin Laden.
Aljazeera has aired a new audiotape it says contains the voice of al-Qaeda's leader, Osama bin Laden. The tape is 11 minutes and 26 seconds long, believed to have been made after March 14, 2006.

According to Aljazeera, in the tape, Bin Laden talks about the "situation in Iraq, Palestine and Sudan" and says that the isolation of the Hamas-led Palestine is a "war by crusaders and Zionists against Islam."

"I say that this war is the joint responsibility of the people and the governments. While the war continues, the people renew their allegiance to their rulers and politicians and continue to send their sons to our countries to fight us. The war goes on and the people are renewing their allegiance to its rulers and masters. 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," said bin Laden.

"The blockade which the West is imposing on the government of Hamas proves that there is a Zionist crusaders war on Islam. I have sworn to only live free. Even if I find bitter the taste of death, I don't want to die humiliated or deceived. The war is a responsibility shared between the people and the governments. They do not want a truce unless it is from our side only. They insist on continuing their crusader campaign against our nation and to loot our wealth," he added.

Bin Laden also talked about Sudan saying, "I call on mujahedeen and their supporters, especially in Sudan and the Arab peninsula, to prepare for long war again the crusader plunderers in Western Sudan. Our goal is not defending the Khartoum government but to defend Islam, its land and its people. The politicians of the West do not want dialogue except for the sake of dialogue to drag us on, for them to gain more time. They want an armistice that is observed only by us."

The United States has since said that they believe the tape is authentic.

"We just heard from the intelligence community that they believe it's authentic," said Scott McClellan, spokesman for the White House.

"We are continuing to take the fight to the enemy abroad and making it difficult for them to plan and plot against Americans. The al Qaeda leadership is on the run and under a lot of pressure. We continue to take all terrorist threats seriously and that is why we are acting on all fronts doing everything within our power to prevail in the war on terrorism," added McClellan.

Aljazeera last aired an audiotape in January by bin Laden, where he promised new terrorist attacks in the U.S. but also offered the U.S. a "long-term truce."