CBS News Correspondent Cami McCormick in Baghdad says authorities are studying the gruesome videotape of the slaying that appeared on the Internet for any clues to the whereabouts of the wanted terrorist. He's believed to be traveling through Iraq.
Brig. Gen. Mark Kimmitt, the top U.S. military spokesman in Iraq, said it may take a while and Zarqawi may have the ability to evade capture -- but he will be caught eventually.
President Bush focused on the Berg slaying in his weekly radio address Saturday, insisting Berg's killers must be hunted down as part of a strategy ultimately designed to bring peace to the U.S.-occupied country.
"We must confront the enemy and stay on the offensive until these killers are defeated," Mr. Bush said in his weekly radio address, as he sought to shift attention from.
With polls showing his approval ratings at the lowest level of his presidency, Mr. Bush went on the offensive in the radio address, saying Marines are systematically dismantling the militia of a radical Shiite cleric and are disrupting enemy attacks in the Fallujah area, home of Saddam Hussein loyalists and other militants.
In the Democrats' weekly radio address, presidential candidate John Kerry lauded American troops in noting Saturday was Armed Forces Day but said the nation must face up to its mistakes.
The United States "has a duty to guarantee that, when mistakes are made, those responsible are held accountable whether they are at the bottom of the chain of command or at the top," the Massachusetts senator said.
"We have a duty to look ahead so that once victory on the battlefield is won, we have a plan to win the peace," he said.
And, he said, the United States has a duty to lead alliances so that the country and its troops will not have to bear "almost alone the burdens of defending freedom."
The high stakes involved in the June 30 handover of government to Iraqis were underscored Friday, when Secretary of State Colin Powell said U.S.-led coalition forces would leave the country in the unlikely event the new interim government should ask them to do so.
White House spokesman Scott McClellan said later that the United States only stations its forces in places around the world "where we are welcome, and I fully expect our forces to continue to be in Iraq at the invitation of a sovereign government on July 1."
Mr. Bush drove home the point in his radio address, declaring that "the vital mission of our military in helping to provide security will continue on July 1st and beyond."
The administration is concluding a week of damage control following the airing late last month of photos showing U.S. soldiers abusing Iraqi detainees at the Abu Ghraib prison originally made infamous as a place of torture under Saddam's regime.
In a swift response, Vice President Dick Cheney questioned whether hundreds of other photos along with some video in the military's hands ought to be released and Defense Secretary Donald Rumsfeld made a surprise visit to the U.S. troops in Iraq. Congress saw the additional pictures, but the public didn't.
The grisly beheading of Berg by killers who said they were avenging the victims in the prisoner abuse scandal became one more argument for keeping the additional pictures of abuse under wraps for now.
"My administration and our military are determined that such abuses never happen again," Mr. Bush said. "All Americans know that the actions of a few do not reflect the true character of the United States armed forces."
Meanwhile, a high school English teacher was placed on leave while school officials investigate complaints that he allowed students to use his classroom computer to view Berg's beheading.
Orange Unified School District officials said Friday they were told that Villa Park High School teacher Stephen Arcudi gave students in two of his English classes the Web site address where they could see video footage of Berg being executed.
"He did not instruct the students to watch it, but apparently he was aware of what was happening and did nothing to stop it," said Assistant Superintendent Cheryl Cohen. "Because of our concern over his judgment and the way he handled the situation, we have put him on leave while we continue to investigate."
Cohen said both a parent and a student complained.
Arcudi, 46, was one of at least three California teachers placed on paid leave Friday for allegedly letting students see the videotape. The other two are employed by the Grossmont Union High School District near San Diego.
Arcudi said he didn't provide the Web address but did discover a student at the start of one of his classes trying to find the Berg video on the Web. He said he discouraged the student from doing so.
But his students said Arcudi did give out the Web address.
"He said: `This is the enemy we're up against and these are the things you don't get to see,"' said Naim Dujak, 17, who added that he watched the beheading.
"People who didn't want to see it, didn't have to see it," Naim said. "He did not force anyone to watch it."
Berg, 26, was remembered at a private memorial Friday marked by heavy security at a Philadelphia-area synagogue.