Warning comes as US commander says extra troop deployment to take longer than expected.
Rasmussen, making his first visit to Moscow since becoming the head of Nato, said: “I would very much like to discuss how we can further Russian engagement in our operation in Afghanistan.”
Medvedev said: “We have many reasons for interaction, many subjects for discussion.
“These are the challenges that exist in the world: terrorism, crime, the need to counter shared threats, regional challenges.”
In particular, Rasmussen said Russia could help by contributing more helicopters.
Referring to his talks with Medvedev, he said: “I suggested a helicopter package. I think Russia could contribute in a very concrete way by providing helicopters, helicopter training and spare parts.”
Sergei Lavrov, Russia’s foreign minister, who also held talks with Rasmussen, said that Medvedev would consider the request.
Relations between Nato and Russia have improved significantly since they were frozen for six months in the aftermath of the August 2008 Russia-Georgia war.
Moscow has repeatedly expressed its willingness to help the war effort in Afghanistan, due to fears that any return to power by the Taliban could destabilise Central Asia and endanger Russia’s own security.
The Kremlin has allowed Nato nations to use its territory for the overland transport of supplies to Afghanistan but ties remain strained over the possible absorption of Georgia and Ukraine into the military alliance.
Russia has objected to the plans, which are in their infancy and not likely to be implemented any time soon, and sees them as Western meddling in its own backyard.
Moscow was expected to raise the issue of creating alternative global security treaties such as a plan recently put forward by Medvedev for an all-embracing Euro-Atlantic agreement.