OSCOW, Sept. 24 ・President Vladimir V. Putin tonight offered the United States broad support for antiterrorist operations in Afghanistan, including opening Russian airspace to relief missions, taking part in some search-and-rescue operations, and arming anti-Taliban forces inside Afghanistan.

Combined with a Russian effort over the weekend to rally Central Asian countries to the American side, the announcement provided crucial support to the international coalition that the White House seeks to build in the wake of this month's terrorist attacks.

It also appeared, after long deliberation and some doubt, to cast Russia's lot firmly in the Western antiterrorism camp. In doing so, Mr. Putin rejected arguments in some military and political circles that the Kremlin was not only inviting the United States into its strategic backyard, but flirting with another war with Islamic militants.

In his brief speech on national television, Mr. Putin said Russia would provide the "active international cooperation" of its intelligence services and supply "weapons and military equipment" to the coalition of forces aligned against the radical Islamic Taliban government in Afghanistan. [Excerpt, Page B2.]

The offer of support appeared to amount to the most decisive alignment of Russia's military and intelligence resources with a campaign led by the United States since the end of the cold war. One chief motive seemed clear: the defeat of Islamic militance in Central Asia, on Russia's southern doorstep.

Mr. Putin said that "it goes without saying that we are prepared to make a contribution" to an international antiterrorist campaign. But he added that the full extent of the cooperation "will directly depend on the general level and quality of our relations with these countries and on mutual understanding in the sphere of fighting international terrorism."

That was a pointed reference to Russia's own problems with Islamic militants in the breakaway province of Chechnya, where the West has repeatedly accused the Kremlin of sanctioning brutality and even criminal behavior by its own troops.

Many Russians believe those tactics to be justified. While they have expressed profound sympathy for the American plight in recent weeks, many also say that the doses of terror in New York and Washington should finally silence American fault-finding with Russian behavior in Chechnya, although there is no indication that Washington's stance has changed.

Mr. Putin said Russia's position had been coordinated with that of Central Asian countries that "do not rule out providing the use of their airfields."

While saying that Russia was ready to open its airspace to help in search-and-rescue operations, he made no mention in his speech of whether Moscow would provide troops to back any American operation to track down the terrorism suspect Osama bin Laden.

But in a meeting with leaders of parliamentary factions before the speech, Mr. Putin was reported to have said that he would not commit Russian troops to operations inside Afghanistan because the Russian Constitution proscribed such operations and the United Nations had yet to authorize them.

Mr. Putin's announcement this evening came after a day in which it became apparent that most Central Asian countries were falling in line behind the American-led clampdown on the Taliban and Mr. bin Laden.

Today, President Narsultan Nazarbayev of Kazakhstan said his nation would employ "all the means it has at its disposal" in the antiterrorist alliance, including the use of airspace and military bases.

American transport planes reportedly landed this weekend near Uzbekistan's capital, Tashkent, unloading reconnaissance equipment and some 200 troops. Turkmenistan, which like Uzbekistan shares a border with Afghanistan, has offered to help with relief missions.

Tajikistan has formally denied reports that American aircraft and troops are at the Kulyab airfield, not 30 miles from the border with Afghanistan, but has otherwise been silent. Russia has roughly 20,000 troops and a major base in Tajikistan, on the Afghan border.

Mr. Putin had spoken with leaders of those and other Central Asian countries this weekend, after meeting with his own security advisers and speaking by telephone with President Bush.

Russian assent to an American presence in the region ・the first American military operations on former Soviet soil, aside from training maneuvers ・is considered crucial to any mission in Afghanistan.

Mr. Putin was explicit about committing military aid to the Northern Alliance, or United Front, led by Burhanuddin Rabbani, whose forces were driven by the Taliban out of power and into a tiny sliver of Afghan land along the Tajik border.

"We are broadening cooperation with the internationally recognized government of Afghanistan headed by Mr. Rabbani and will render additional aid to its armed forces in the form of the supply of weapons and military equipment," Mr. Putin said.

The coalition fighting the Taliban includes the forces that defeated Soviet troops in Afghanistan more than a decade ago, but they are now seen in Moscow as the most effective means to defeat Islamic radicalism.

A senior American official said Mr. Putin appeared to view the terrorist crisis as a chance to achieve two important goals. One is to rebuild relations with the United States, which have been in tatters since the Americans bombed Yugoslavia in the 1999 Kosovo campaign. The second is to enlist Washington in its own cause of defeating the Taliban, which the Kremlin believes has helped militants in Chechnya.

As for the White House, it got most if not all of what it needed and expected from Mr. Putin, the American official said, led by political support for Central Asian military operations and the symbolic importance of support from Russia, an old enemy and still distant friend.

Mr. Putin's decision is not without political risk, illustrated by his choice to coordinate international antiterrorist actions: Sergei Ivanov, his defense minister.

Mr. Ivanov argued only a week ago that it was unthinkable that troops from NATO nations would be allowed on former Soviet territory. A longtime Putin adviser, he may only have been dutifully reflecting the conservatism of the military establishment here, much of which remains deep-frozen in the cold war.

But it remained to be seen how enthusiastically Mr. Putin's orders for military and intelligence cooperation are executed at lower levels.