Al Qaeda leader Osama bin Laden has appeared on a new videotape, directly admitting to organizing the Sept. 11, 2001 attacks and threatening more attacks to come.

Al-Jazeera broadcast parts of the 18-minute-long tape Friday evening, which begins with an address to the American population.

"O American people, I am speaking to tell you about the ideal way to avoid another Manhattan, about war and its causes and results," an apparently healthy bin Laden says, reading from a sheet of paper.

In his clearest comments yet taking responsibility for the 9/11 attacks, bin Laden says the attacks were carried out because "we are a free people. And if you're going to destroy our freedom, we're going to destroy yours."

"God knows it did not cross our minds to attack the towers, but after the situation became unbearable and we witnessed the injustice and tyranny of the American-Israeli alliance against our people in Palestine and Lebanon, I thought about it."

He says the attacks would have been less severe if U.S. President George Bush had been more alert.

"It never occurred to us that the commander in chief of the country would leave 50,000 citizens in the two towers to face those horrors alone ... because he thought listening to a child discussing her goats was more important," bin Laden said, referring to Bush's visit to a school when the attack occurred.

Speaking just days ahead of the U.S. presidential election, he then says the United States could face new attacks because, he says, the reasons for mounting the Sept. 11 strikes still exist.

"Despite entering the fourth year after Sept. 11, Bush is still deceiving you and hiding the truth from you and therefore the reasons are still there to repeat what happened," bin Laden tells Americans.

In words that suggest the tape was made fairly recently, bin Laden adds:  "Your security is not in the hands of (Democrat Sen. John) Kerry or Bush or al Qaeda. Your security is in your own hands. And each state that does not harm our security will remain safe."

Despite the angry rhetoric, the video does not appear to contain a specific threat against American targets.

This is the first video of the al Qaeda leader to surface in two years, though audio tapes of his voice have surfaced since. But in none of his previous messages has bin Laden directly stated that he planned 9/11.

It also appears the U.S. government hoped the tape would never be seen.

Before the tape was aired, the State Department asked the government of Qatar to discourage Al-Jazeera from broadcasting it, a senior State Department official said.

Al-Jazeera did not say how it received the tape. The Qatari-based channel has previously received audio and videotapes from people linked to al Qaeda.

Bush responded to the tape before  boarding Air Force One in Toledo, Ohio by vowing that "Americans will not be intimidated or influenced by an enemy of our country... We are at war with these terrorists and I'm confident we will prevail."

Sen. Kerry responded by vowing to "stop at nothing" to hunt down bin Laden. But he also used the oppurtunity to take a swipe at Bush, blaming him for not using American forces to hunt bin Laden down in the Tora Bora mountains in late 2001.

"He didn't choose to use American forces to hunt down Osama bin Laden," Kerry said in an interview with a Milwaukee radio station. "He outsourced the job."

"I believe I can run a more effective war on terror than George Bush," Kerry asserted.

Bush later responded at an Ohio rally: "My opponent continues to say things he knows are not true."

"It's the worst kind of Monday-morning quarterbacking."