Elusive al-Qaeda chief Osama bin Laden mocked the United States as "weak" and vowed to escalate fighting in Iraq in a new video, his first such appearance in nearly three years.

The al-Qaeda leader discusses current events but issues no direct threats in the video, released Friday. His appearance appears to be timed to mark the upcoming sixth anniversary of the September 11, 2001

attacks on New York and Washington.

Bin Laden appears with his beard trimmed and apparently dyed black to hide streaks of gray seen in previous footage.

There are two ways to end the Iraq war, bin Laden says, according to a transcript released by the US-based SITE Intelligence Group which monitors Islamic militant websites. "The first is from our side, and it is to continue to escalate the killing and fighting against you," says bin Laden.

The second is to do away with the US democratic system of government, which he says merely serves the interests of major corporations.

In the rambling message bin Laden attacks US President George W. Bush, the US neoconservative thinkers that support him and global corporations for fomenting the Iraq war. He also attacks the US Democratic Party, which he claims has done little to halt the war, makes references to global capitalism and climate change, and invites Americans to embrace Islam.

US intelligence agencies confirmed the tape's authenticity. "I think people are pretty confident it is his voice," said a US intelligence official, speaking on condition of anonymity.

The tape was probably produced as recently as early August because of a reference to the 62nd anniversary of the bombing of Hiroshima on August 6, the official said.

It is bin Laden's first such appearance since October 2004, when he threatened new attacks against the United States in a video just days before US presidential election.

Bush used the tape to bolster the case for continued US military presence in Iraq.

"The tape is a reminder about the dangerous world in which we live," said Bush, who was attending the Asia Pacific Economic Cooperation summit Sydney.

"I find it interesting that Iraq was mentioned, which is a reminder that Iraq is a part of this war against extremists," he said.

"If al-Qaeda bothers to mention Iraq, it's because they want to achieve their objectives in Iraq, which is to drive attacks and develop a safe haven," Bush said.

"And the reason they want a safe haven is to launch attacks against America or any other ally. And therefore it's important that we show resolve and determination to protect ourselves, deny al-Qaeda safe haven and support young democracies, which will be a major defeat for their ambitions," he said.

Earlier Friday CIA Director Michael Hayden warned that al-Qaeda was planning new, large-scale attacks on US targets.

"Our analysts assess with high confidence that al-Qaeda's central leadership is planning high impact plots against the American homeland," he said in a New York speech, giving no further details.

With a brown wall as a backdrop, bin Laden appears in the tape wearing a white robe topped by a beige cloak, similar to the traditional dress of men in the Gulf region, and looked more like a Muslim cleric than a fighter.

In a voice and tone similar to those heard in previous videotapes, bin Laden taunts the United States for its troubles in Iraq and the effect of the September 11, 2001 attacks.

"Despite America being the greatest economic power and possessing the most powerful and up-to-date military arsenal as well ... 19 young men were able -- by the grace of Allah, the most high -to change the direction of its compass," he said in a reference to the September 11 hijackers.

"America is weak despite its apparent strength," he says.

Widely believed hiding in the remote tribal areas along the Pakistan-Afghanistan border, bin Laden has evaded capture despite a huge US manhunt and a 25-million dollar bounty on his head.

According to the video transcript, bin Laden begins with "praise to Allah" and his "law of retaliation" -- "an eye for an eye, a tooth for a tooth and the killer is killed."

Bush is "like the one who ploughs and sows the sea: He harvests nothing but failure," bin Laden said.

In the tape bin Laden also mentions French President Nicolas Sarkozy, elected in May, and British Prime Minister Gordon Brown, who took office in June.