CAIRO -- Al Qaeda's second in command hailed the London suicide bombings yesterday, warned Britain that more destruction lies ahead, and promised tens of thousands of US casualties in Iraq in a brazen assertion of the terror group's global reach.
Ayman al-Zawahri also renewed terrorist threats to other countries with troops in Iraq and Afghanistan, asserting they had shunned Osama bin Laden's offer last year of a truce if foreign forces left the battleground.
In the tape, parts of which were broadcast by Al-Jazeera, Zawahri made no direct claim that Al Qaeda carried out the July 7 attacks in the British capital, but sought instead to blame the carnage on Prime Minister Tony Blair's decision to deploy and keep troops in Iraq. Britain maintains 8,500 forces mainly in southern Iraq.
''Blair has brought to you destruction in central London, and he will bring more of that, God willing," Zawahri said.
President Bush dismissed Zawahri's threat, saying, ''We will stay on the offense against these people. They're terrorists and they're killers, and they will kill innocent people . . . so they can impose their dark vision on the world."
In London, Blair's Downing Street office declined to comment.
Jeremy Bennie, a terrorism analyst for Jane's Defense Weekly, said Zawahri appeared to be trying to put an Al Qaeda stamp on the July 7 attacks on the London transit system. The bombings killed 56 people, including four attackers.
''He has tacitly taken responsibility by claiming Al Qaeda is in control of the situation, even as most people aren't really sure bin Laden and al-Zawahri still are capable of organizing such an attack," Bennie said by telephone.
Yesterday marked the seventh time Zawahri has used videotapes or audiotapes 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 -- home to two of Islam's holiest shrines.
Zawahri issued the fresh threats with a Kalashnikov rifle propped against a woven cloth background that moved with the wind and showed the sunlight, suggesting the scene was filmed outdoors.
He wore a white robe and black turban and emphatically wagged his finger 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 Zawahri. The Prophet Mohammed and his followers wore black turbans during their invasions in the Arabian Peninsula, he said.
Zawahri is ''exploiting the whole atmosphere following London and Sharm el-Sheik explosions to carry out the sort of instigation that propels more operations," 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 Iraq insurgency led by bin Laden's Jordanian comrade Abu Musab al-Zarqawi continues to kill Iraqis and Americans, Zawahri vowed 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.
''If you go on with the same policy of aggression against Muslims, you will see, God willing, what will make you forget the horrible things in Vietnam," he said.
''There is no exit from Iraq except in immediate withdrawal. Any delay in taking that decision means nothing but more dead, more losses," he said. ''If you don't leave today, certainly you will leave tomorrow, but after tens of thousands of dead and double the number of disabled and wounded."
Zawahri threatened other nations who have sent troops alongside US forces in Iraq and Afghanistan, saying they ''will harvest the fruits of their cooperation soon, God willing."
He also called for Arab militaries, intellectuals, and businessmen to start working to get rid of ''corrupt" regimes in the Middle East and ''start preparing for change, starting now, whatever it takes of time or effort."