The announcement by a top Kremlin aide came ahead of President Obama's visit to Moscow next week, when the deal is expected to be signed.

Russia has been allowing the United States to ship nonlethal supplies across its territory for operations in Afghanistan, and Kremlin officials had suggested further cooperation was likely.

Kremlin foreign policy adviser Sergei Prikhodko told reporters that the expected deal would enable the United States to ship lethal cargo and would include shipments by air and land.

He said it was unclear if U.S. soldiers or other personnel would be permitted to travel through Russian territory or airspace.

"They haven't asked us for it," he said.

The normal supply route to landlocked Afghanistan via Pakistan has come under repeated Taliban attack, and the United States and NATO have been eager to have an alternate overland supply route through Russia and the Central Asian countries.

Confirmation of such a deal appeared aimed at setting a constructive tone for the meetings between Obama and Russian President Dmitry A. Medvedev on Monday and Tuesday. After years of increasing strain, both governments have expressed hope that the summit will put ties between the former Cold War rivals back on track.

Military analyst Alexander Golts, however, said the United States should be under no illusion about Russia's intentions. Although Medvedev has set a warmer tone in relations with the West, his predecessor, Vladimir V. Putin, retains considerable power as prime minister.

"The least impression you should get from this is that Putin's foreign policy style foresees gestures of goodwill," Golts said.

The Russian leadership still has the mind-set of "19th-century Realpolitik" and seeks the ability to hold its partners "by the throat," he said.

"If something goes wrong in Russian-U.S. relations, this transit will cease as quickly and suddenly as it started," Golts said.

While Russia has stressed a willingness to work with the West to bring stability to Afghanistan, it has shown that it can use its clout in the former Soviet republics of Central Asia to hobble U.S. efforts.

Russia was seen as the instigator of Kyrgyzstan's decision earlier this year to evict the United States from an air base used to ship military hardware and troops to Afghanistan. The decision was reversed only after the United States agreed to pay three times the price.

No comment was immediately available from the Pentagon yesterday, a federal holiday.

The expected deal would be the first time Russia has allowed U.S. military shipments through its territory during the Afghan campaign, said Fyodor Lukyanov, editor of Russia in Global Affairs magazine. "This may actually be the first time they will do this since World War II," he said.