The United States is condemning the school takeover in Russia as a "particularly barbaric" act of terrorism. It says the perpetrators bear all the blame for the casualties.

U.S. reaction to the tragedy in North Ossetia was led by President Bush, who departed from scripted remarks at a campaign rally in the midwestern state of Wisconsin to condemn the schoolhouse takeover, and stress U.S. solidarity with Russia against terrorism.

"This is yet another grim reminder of the length to which terrorists will go to threaten the civilized world. We mourn the innocent lives that have been lost," he said. "We stand with the people of Russia. We send them our prayers in this terrible situation."

President Bush had telephoned Russian President Vladimir Putin when the hostage episode began on Wednesday, and was briefed by aides on the carnage that ended the standoff in between campaign events Friday.

The United States has in the past been critical of Moscow's handling of the Chechen conflict, as recently as this week complaining "serious flaws" in elections there Sunday that produced a landslide victory for Kremlin-backed presidential candidate Alu Alkanov.

However, officials in Washington have made clear that no political cause can justify the terrorist acts committed in recent days in the name of the Chechens.

At a news briefing here, State Department Richard Boucher said the United States absolutely condemns the hostage taking in North Ossetia and said blame for the deaths and injuries rests entirely with the perpetrators:

"This was a particularly barbaric act of terrorism that put at risk the lives of dozens of children as well as parents and teachers," Mr. Boucher added. "The blame for the tragedy lies squarely with the terrorists. There's no cause that can justify these kinds of terrorist acts."

Mr. Boucher had no comment on the use of force by Russian authorities to try to end the siege, saying the United States is not about to "second guess" Moscow's handling of the episode.