Al Qaeda deputy leader Aymen al-Zawahiri (search) marked the four-week anniversary of the deadly blasts in London's transit system by threatening more attacks on London and against the United States.
Al-Zawahiri, in a tape shown on the Al-Jazeera (search) satellite channel, warned that terrorists would strike again unless England and the United States withdraw troops from Iraq.
"As for you, the Americans, what you have seen in New York and Washington, what losses that you see in Afghanistan and Iraq, despite the media blackout, is merely the losses of the initial clashes," he said, referring to the Sept. 11 attacks blamed on Al Qaeda.
"If you go on with the same policy of aggression against Muslims, you will see, with God's will, what will make you forget the horrible things in Vietnam and Afghanistan."
In response, President Bush, speaking from his Crawford, Texas, ranch where he hosted Colombian President Alvaro Uribe, said the United States will not be swayed by such threats.
"We will stay the course. We will complete the job in Iraq," Bush said.
"We're defeating the terrorists in a place like Iraq so we don't have to face them here at home," Bush said. "We're spreading democracy and freedom to parts of the world that are desperate for democracy and freedom. ... The comments by the No. 2 man of Al Qaeda make it clear that Iraq is a part of this War on Terror."
Describing a clash of ideologies, "freedom vs. tyranny," Bush said: "We have had these kinds of clashes before and we have prevailed. We have prevailed because we're right. We have prevailed because we adhere to a hopeful philosophy, and we have prevailed because we would not falter."
The new terror tape was being examined to determine its authenticity, but according to officials there has never been an al-Zawahiri tape that was not real. The tape appears to have been made recently given the references to last month's London transit bombings.
Taahir Hoorzook, of the media relations department in Al-Jazeera, said the broadcaster received the tape Thursday.
"It was left at one of our offices, and we got it from there," he said, declining to name the location of the office.
The tape is about five minutes long and Al-Jazeera aired only 10 percent of it, he said. "The content of the rest of the tape which we didn't air, is the usual rhetoric, speaking about the Islamic lands occupied and stuff like that which we found not newsworthy," Hoorzook said.
The Al Qaeda leader, second in the organization behind Usama bin Laden, said British Prime Minister Tony Blair (search) is to blame for the attacks in London.
"Blair has brought to you destruction in central London, and he will bring more of that, God willing," al-Zawahiri said in the tape, referring to the July 7 attacks that killed 56 people as well as the attempted July 21 attacks on London's subways and buses.
He continued: "As to the nations of the crusader alliance, we have offered you a truce if you leave the land of Islam.
"Hasn't Sheik Usama bin Laden told you that you will not dream of security before there is security in Palestine and before all the infidel armies withdraw from the land of Muhammed?" al-Zawahiri added.
In London, Blair's Downing Street office declined to comment on the broadcast. Britain maintains 8,500 forces mainly in southern Iraq.
Al-Zawahiri appeared also to be referring to the terror attacks in Madrid, Spain, last year that were linked to Al Qaeda (search).
"Our message is clear: You will not be safe until you withdraw from our land, stop stealing our oil and wealth and stop supporting the corrupt rulers," al-Zawahiri said.
Thursday marked the seventh time al-Zawahiri has used a videotape or audiotape to speak for Al Qaeda since the Sept. 11, 2001, attacks in the United States. The latest appearance followed the Egyptian physician's pattern of issuing threats of further death and destruction if the United States and its allies in Iraq and Afghanistan refuse to withdraw troops from the region, including Saudi Arabia, which is home to two of Islam's holiest shrines.
The tape showed al-Zawahiri positioned in front of a woven cloth that moved with the wind and showed the sunlight, indicating it appeared to be made outdoors. He was wearing a white robe and a black turban and emphatically wagged his finger at the camera while speaking.
The black turban — a change from the white turban he has worn in past videos — is "a sign that it's time of war," said Montasser el-Zayat, an Egyptian attorney who defends Islamic radicals and who spent three years in prison with al-Zawahiri. The prophet Muhammad and his followers wore black turbans during their invasions in the Arabian Peninsula, he said.
Al-Zawahiri is "exploiting the whole atmosphere following London and Sharm el-Sheik explosions to carry out the sort of instigation that propels more operations," el-Zayat said. At least 64 people were killed in the July 23 attacks in the Egyptian Red Sea resort of Sharm el-Sheik.
As the Iraqi insurgency led by bin Laden's Jordanian comrade Abu Musab al-Zarqawi continues to kill Iraqis and Americans, al-Zawahiri promised more savagery.
"What you have seen in New York and Washington, you Americans, and the losses you see in Afghanistan and Iraq — despite all the media blackout — are merely the losses from the initial clashes," he said.
He continued, "The truth that has been kept from you by [President] Bush, [Secretary of State Condoleezza] Rice and [Defense Secretary Donald H.] Rumsfeld is that there is no way out of Iraq without immediate withdrawal, and any delay on this means only more dead, more losses.
"If you don't leave today, certainly you will leave tomorrow, and after tens of thousands of dead, and double that figure in disabled and wounded."
Referring to the Western nations contributing troops to the U.S.-led coalition in Iraq, he said: "As to the nations of the crusader alliance, we have offered you a truce if you leave the land of Islam. ... Instead [of accepting the truce], you spilled blood like rivers in our countries and we exploded the volcanoes of wrath in your countries."
In June, Al-Jazeera broadcast a videotape of al-Zawahiri disparaging the U.S. concept of reform in the Middle East and saying armed jihad is the only way to bring change in the Arab world.
Al-Zawahiri, an Egyptian doctor who merged his militant faction with that of bin Laden in Afghanistan in the late 1990s, spoke with a Kalashnikov rifle propped up behind his right shoulder against a plain background.
Analysts said that al-Zawahiri, who has been in hiding since the United States invaded Afghanistan in late 2001, is reminding the world Al Qaeda remains a threat.
"He's a fear amplifier," said Bob Scales, a retired Army major general and a FOX News military analyst. "His purpose is to take a tragic event and make the most of it."
Scales said al-Zawahiri was trying to "give some assurance to others in the Arab world that Al Qaeda is in charge and, frankly, try to extend or expand the psychological effects of what's happened for the benefit of Al Qaeda."
The Associated Press contributed to this report.