Russia will allow the US to ship weapons across its territory to Afghanistan, a top Kremlin aide said on Friday in a gesture aimed at bolstering US military operations and improving strained ties between Washington and Moscow.

The deal is expected to be signed during President Barack Obama's visit to Moscow next week, Kremlin foreign policy adviser Sergei Prikhodko said.

Russia has been allowing the US to ship non-lethal supplies across its territory for operations in Afghanistan and Kremlin officials had suggested further cooperation was likely.

Prikhodko told reporters that the expected deal would enable the US to ship lethal cargo and would include shipments by air and land.

He said it was unclear if US 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 US 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 Presidents Barack Obama and Dmitry Medvedev on Monday and Tuesday.

After years of increasing strain, both governments have expressed hope the summit will put ties between the former Cold War rivals back on track.

Serious rifts remain over other defence issues. The US and Russia want to forge a nuclear arms reduction agreement to replace the 1991 START treaty, which expires in December.

But talks on a new treaty are complicated by Russia's push for the US to scrap the previous administration's plans for missile defence facilities in Eastern Europe.

The US says missile interceptors based in Poland and a related radar in the Czech Republic - if built - would be aimed to counter a potential Iranian threat and would not threaten Russia. Russia rejects those arguments and says the facilities would be aimed to weaken Russia's nuclear deterrent.

Prikhodko said Medvedev and Obama are expected to sign a declaration of understanding that would set out guidelines for a new arms reduction treaty and would likely include specific target numbers.

He insisted that plans for further nuclear arms cuts and a possible US missile shield in Europe are inextricably linked and that Russia wants the Obama administration to acknowledge that.

US officials have rejected Russia's argument that cuts on offensive weapons must be linked with US plans for missile defence.

"We would like the interconnection between START and missile defence to be described" in the declaration signed at the summit," he said.

Prime Minister Vladimir Putin's spokesman also said that the two issues are interconnected and indicated Russia's leaders would repeat their arguments in meetings with Obama, who is to hold talks with Putin as well as Medvedev.