Russia today announced that it has once again sealed off the border of Chechnya in an effort to contain a guerrilla incursion into neighboring Dagestan, but a top official said it would be a mistake to launch a ground offensive against the Chechens.

Russia has massed an estimated 20,000 troops along the border between the breakaway southern region and the rest of the country, and has been carrying out daily bombing raids inside Chechnya aimed at the Islamic rebels. But Deputy Interior Minister Igor Zubov said a ground attack would extract a heavy price.

"I can say that the federal forces are ready for such an operation as far as morale and combat readiness are concerned," he told reporters. "But first a political decision should be made--and it is not a decision we should make."

Zubov said a ground operation "will involve heavy losses," recalling the hundreds of soldiers killed in the past two months in Dagestan, and the tens of thousands of lives lost in the two-year Chechen war for independence that ended in a stalemate in 1996.

He said Russia's tactics are to seal the border with Chechnya and bomb the region, which he described as "contactless destruction" of the guerrillas' bases.

Although Russia has sought to close off the border with Chechnya before, this is the first time such a large amount of men and armor has been stationed on the ground. Chechnya also shares a border with Georgia, which is not being patrolled by the Russians.

The border was ordered sealed after a series of incursions by Chechen rebels into Dagestan, which led to combat with Russian forces and was followed by four apartment-house bombings in which nearly 300 people--almost all of them civilians--were killed. Russia has accused the Chechen fighters of ordering the explosions, which they deny.

As in the past, part of the problem for Russia in trying to cut off Chechnya is that the border runs through mountainous terrain that is difficult to police. But Zubov claimed that "there can be no undetected crossing of the border by large forces from Chechen territory" now that Russian troops are in place.

Russian military officials have said that airstrikes are continuing, with about 30 sorties a day. This is the most intense combat with Chechnya since the 1996 cease-fire, which deferred a decision on Chechnya's status for five years.