Updated

The chief U.S. security officer posted in Moscow has joined Russians in a command center near the Moscow theater where at least two Americans are among about 600 hostages held by Chechen militants.

The posting of the U.S. Embassy's security chief implements a promise President Bush made by telephone Thursday, an offer of support and assistance to Russian President Vladimir Putin.

So far, Russia has requested no specific help, U.S. officials said, as they anxiously tracked developments at the theater, where Muslim militants from the rebellious Chechnya region have threatened to start killing their captives at a dawn Saturday unless their demands are met. Those are that the Russian government agrees to stop its long war to suppress the Chechnya uprising and begin to withdraw Russian troops.

The State Department said at least two Americans were among the 75 foreign hostages.

Two women among the Chechens wore robes with Arabic script on the head coverings.

However, a State Department spokeswoman, Brenda Greenberg, said, "At this time we have no direct evidence of an Al Qaeda link to this incident, but information about the terrorists remains sketchy."

A Chechen fighter connected to the extremist wing of the Chechen separatist movement, some of whose members are known to have terrorist affiliations, appears to be the leader of the hostage-holders, she said.

Assignment of the embassy's security chief was disclosed by another U.S. official, who spoke on condition of anonymity.

Apart from his expertise, the security chief would be in a position to share information with the Russians.

In Moscow, U.S. Ambassador Alexander Vershbow called the captors "terrorists" and said they should release everyone "immediately and without conditions."

According to the ambassador, three U.S. citizens and a Russian citizen holding U.S. permanent residence status were among the hostages.

There was no explanation of the different count given Friday by the State Department.

Bush's quick offer of U.S. help to Putin paralleled the prompt expression of condolences the Russian president conveyed after the Sept. 11, 2001, terror attacks on the United States.

He was the first foreign leader to reach Bush after the deadly New York, Washington and Pennsylvania incidents, and their relationship was warmed as a result.

Still, the State Department indirectly criticized the Russian government Friday for its approach to Chechen separatists.

"The lack of a political solution and the number of credible reports of massive human rights violations unfortunately helped create a favorable environment for terrorism," spokeswoman Greenberg said.

"We repeatedly have stressed there can be no military solution to the Russia-Chechnya conflict," she said. "It remains our belief that a political settlement is the only means of bringing a lasting peace to the region and denying terrorists an excuse for terrorist acts."

The department also said the Chechen people have legitimate grievances, issues and concerns, but engaging in terror in pursuit of legitimate political objectives only discredits the cause.

U.S. citizens were advised by the State Department in early October to avoid travel to Chechnya. The advisory remains in effect, but no new warnings were issued after the theater takeover.