American officials also say they believe that Iran and Russia want to insure that many of the planned Caspian oil pipelines traverse Iranian or Russian territory. As a result, the Iranians, and to a lesser extent the Russians, have an incentive to block efforts to build pipelines across Afghanistan to the Indian subcontinent.

With peace talks stalled and the two sides gearing up for more war, frustrated executives from Western oil companies appear to be playing a more active role as mediators than the Clinton Administration is. Unocal Corporation, which leads a consortium that hopes to build a pipeline to transport natural gas and oil from Turkmenistan through Afghanistan to Pakistan, is financing a University of Nebraska program to train Afghan workers and teachers in regions controlled by both sides, and has paid for Taliban members to visit the United States. Bridas Corporation, an Argentine company that is a Unocal rival with its own plans for an Afghan pipeline, also has representatives in the country trying to cultivate both northern alliance and Taliban leaders.

Yet Unocal and Bridas executives have said they cannot proceed until the fighting ends and an internationally recognized government is established.

Moscow denies that it is arming the Afghan rebels, and Mr. Massoud has said in interviews that he receives much of his equipment from the Russian mafia, not the Russian Government. American officials believe that the rebels do acquire equipment on the international arms market, but are still convinced that both the Russian and Iranian Governments are directly involved.

In fact, American intelligence officials say that both the northern alliance and the Taliban now field such impressive arsenals that they could not acquire, maintain and operate them without foreign assistance. Both sides have hundreds of T-54 and T-62 Russian-designed tanks, along with towed artillery, multiple-rocket launchers, and MIG-21 and SU-17 fighter aircraft, according to United States intelligence estimates.

While the abundance of surplus weaponry left over from the Soviet-supplied Afghan Army is being used by both the rebels and the Taliban, the demands for spare parts, maintenance and training have forced the two sides to seek outside support.

American officials and others say Mr. Massoud's rebel faction, perhaps the most formidable single group opposing the Taliban, now has a major supply center at an air base in neighboring Tajikistan, a former Soviet republic where some 20,000 Russian troops are stationed and where Moscow retains enormous influence.