Suspected terror mastermind Usama bin Laden is trying to acquire nuclear weapons, President Bush said Tuesday, confirming what many have fearfully speculated about since Sept. 11.

"These terrorist groups seek to destabilize entire nations and regions. They're seeking chemical, biological and nuclear weapons. Given the means, our enemies would be a threat to every nation; and, eventually, to civilization itself," Bush said via satellite broadcast to a 20-nation gathering of Eastern European leaders.

Later, the president said he was making that charge using bin Laden's own assertion from a couple of years ago that it was his religious duty to acquire weapons of mass destruction.

Officials said they have no evidence bin Laden already has such weapons, but the president said he wouldn't wait for the authors of mass murder to obtain weapons of mass destruction.

The president also reiterated his call for other countries to support the war.

"No nation can be neutral in this conflict, because no civilized nation can be secure in a world threatened by terror," Bush said.

Previewing his weekend speech to the Warsaw Conference on Terrorism, Bush said he was putting "every nation on notice" that their support for ending terrorism must "involve more than sympathy or words."

"Our enemies have brought only misery and terror to the people of Afghanistan. And now they are trying to export that terror throughout the world. Al Qaeda operates in more than 60 nations, including some in Central and Eastern Europe," Bush said.

He issued a long indictment of the Taliban regime and its terrorist allies: They kill, then rejoice over the murders; steal food from their own people; destroy religious monuments; forbid children to fly kites, sing songs or build snowmen. A girl of 7, Bush said, can be beaten for wearing white shoes.

Bush compared Afghanistan's Taliban regime and its "mad global ambitions" to the totalitarian regimes that enslaved Europe for much of the last century, and asked the region's new leaders to join his anti-terrorism campaign.

Invoking the communist history that closed off freedoms to many of the nations assembled, Bush tip-toed around inciting allies who continue to have strong communist parties, like Russia and other former Soviet nations.

"For more than 50 years, the people of your region suffered under repressive ideologies that tried to trample human dignity. Today our freedom is threatened once again," Bush said. "Like the Fascist totalitarians before them, these terrorists — Al Qaeda, the Taliban regime that supports them and other terror groups across the world — try to impose their radical views through threats and violence."

"We see the same intolerance of dissent, the same mad global ambitions, the same brutal determination to control every life and all of life. We have seen the true nature of these terrorists in the nature of their attacks," Bush said.

The Warsaw conference was assembled at the invitation of Polish President Aleksander Kwasniewski as part of a 10-day diplomatic offensive designed to address doubts about the military campaign in Afghanistan and discuss ways Eastern and Central European nations can cooperate in fighting terrorism.

Heads of state from Albania, Bosnia, Croatia, Estonia, Latvia, Lithuania, Moldova, Romania, Slovakia, Ukraine and Macedonia confirmed participation, said Andrzej Majkowski, a senior aide to Kwasniewski.  The Czech Republic, Slovenia and Yugoslavia planned to send senior government representatives, he said.

Hungary also was expected to participate, but had not decided whom to send. Observers were expected from Russia, Belarus, Turkey, the European Union, NATO and the Organization for Security and Cooperation in Europe.

Bush avoided making promises of reciprocity for support in the war on terror. Many of the nations in attendance are seeking entry into NATO.

His early morning address was given even before his weekly breakfast meeting with congressional leaders. That meeting was expected to focus on reconciling House and Senate versions of an airline safety bill.

Bush was meeting later with French President Jacques Chirac and Serbian Prime Minister Zoran Djindjic. Wednesday, Bush is scheduled to meet British Prime Minister Tony Blair. Friday, he will meet Indian Prime Minister Atal Bahari Vajpayee.

The Associated Press contributed to this report.