Mr Gorbachev, who pulled Russian troops out of Afghanistan in 1989 after a 10-year war, said the US had no alternative but to withdraw troops.
"Victory is impossible in Afghanistan. [Barack] Obama is right to pull the troops out. No matter how difficult it will be," he told the BBC.
Mr Gorbachev added that as the Soviets prepared to withdraw from Afghanistan, the US was training militants, "the same ones who today are terrorising Afghanistan and more and more of Pakistan".
He said that because of this, withdrawal would be more difficult.
"But what's the alternative - another Vietnam? Sending in half-a-million troops? That wouldn't work."
His comments came amid news that Dmitry Medvedev, the Russian president, will attend a Nato summit next month, to discuss plans for Russian forces to return to Afghanistan.
Nato officials said Russia had agreed to sell helicopters to Afghanistan and provide training.
Moscow will allow Nato forces to withdraw equipment from Afghanistan overland for the first time, in proposals expected to be agreed in Lisbon.
"The summit can mark a new start in the relationship between Nato and Russia," said Anders Fogh Rasmussen, the Nato secretary-general.
"We will hopefully agree on a broad range of areas in which we can develop practical co-operation on Afghanistan, counter-terrorism, counter-narcotics."
He also said that British and US troops would remain on Afghanistan's front lines for years under an open-ended agreement to be signed at the summit. Hamid Karzai, the Afghan president, has demanded that his forces take over the fight against the Taliban by 2014.
While his call has been embraced by Western leaders, including Prime Minister David Cameron who set a five-year deadline on the Army's combat role, Mr Rasmussen said troops would not be withdrawn immediately.
Under a blueprint drawn up by Gen David Petraeus, Nato commander in Afghanistan, foreign troops would "thin out" but not leave disputed territory.
