On the same day, President Bush said that the United States will work for the return of captive Americans in Iraq, but will not submit to terrorist tactics. "We, of course, don't pay ransom for any hostages," Mr. Bush said.
"What we will do, of course, is use our intelligence-gathering to see if we can't help locate them," Mr. Bush said.
The video, the authenticity of which could not be immediately confirmed, also bore the logo of the Islamic Army in Iraq and showed a U.S. passport and an identification card that identified him as Ronald Schulz, CBS News correspondent Kimberly Dozier reports. The video says that unless all Iraqi prisoners are released,
If true, the man would become the second American taken hostage in the last two weeks. A U.S. citizen was among four peace activists taken hostage on Nov. 27 by a group calling itself the Swords of Righteousness. Two Canadians and a Briton were also part of that group.
A French engineer was taken hostage in Baghdad on Monday and a German aid worker was abducted near Mosul on Nov. 26.
Police Maj. Falah al-Mohammadawi said he didn't have any additional information Tuesday about the kidnapping of the French engineer, Bernard Planche, but that the Interior Ministry had distributed Planche's photo to all the checkpoints around Baghdad.
In London, British Foreign Secretary Jack Straw on Monday encouraged the kidnappers of the Briton to make contact, saying "we stand ready to hear what they have to say."
The British Broadcasting Corp. cited a Western diplomat in Baghdad as saying direct contact had been made with the hostage-takers. It did not identify the diplomat.
Straw, however, underlined the British government's refusal to negotiate with kidnappers or pay ransom.
There is no evidence the kidnappings were coordinated, and those responsible for abducting the German aid worker and four Christian peace activists claim to represent different groups. But the incidents do seem timed to coincide with Saddam's trial or the Dec. 15 elections.
Christian Peacemaker Teams issued another statement Tuesday, appealing to the kidnappers to release the four activists.
"As you can see by the statements of support from our friends in Iraq and all over the world, we work for those who are oppressed," the group said. "We also condemn our own governments for their actions in Iraq."
Mustafa Alani, director of security and terrorism studies at the Gulf Research Center in Dubai, United Arab Emirates, said he thinks the sudden increase is not an accident.
"There is some sort of policy to go back to kidnappings," he said. "The elections are coming and these groups want attention and publicity. That way their political statement will get a priority in the Western media."
Mr. Bush, speaking to reporters at the end of an Oval Office meeting with the director-general of the World Health Organization, would not comment on reports that the United States runs secret prisons abroad.
"I don't talk about secret programs," Mr. Bush said.
But, he said, the United States does not torture and will do everything in its legal power to protect Americans while abiding by U.S. law.
Human rights organizations and legal groups, both in the U.S. and abroad, have accused the United States of allowing a practice known as "rendition to torture," in which suspects are taken to countries such as Egypt and Saudi Arabia where harsh interrogation methods are used. The U.S. has denied that tactic, a denial Mr. Bush repeated Tuesday.
"We do not render to countries that torture," he said.
Secretary of State Condoleezza Rice, who is traveling in Europe, has faced tough questions about whether the United States houses suspected terrorists in secret prisons that violate European legal and human rights guarantees. The general issue of U.S. treatment of detainees in the war on terror has been an irritant in relations with Europe and other parts of the world since shortly after the Sept. 11, 2001, attacks.
It gained new immediacy last month with a Washington Post report claiming the U.S. ran prisons in Thailand, Afghanistan and Eastern Europe, and claims by Human Rights Watch that it had tracked CIA flights into Eastern Europe.
Mr. Bush said the best way to make Iraq a peaceful society is to continue to spread democracy.
"There are terrorists there who will kill innocent people and behead people and kill children, terrorists who have got desires to hurt the American people," he said. "The more violent they get, the clearer the cause ought to be, that we're going to achieve victory in Iraq and that we'll bring these people to justice. We will hunt them down, along with our Iraqi friends, and at the same time spread democracy."