The former leader of the Soviet Union, Mikhail Gorbachev, has warned Nato that victory in Afghanistan is "impossible".
Mr Gorbachev said that the US had no alternative but to withdraw its forces if it wanted to avoid another Vietnam.
As Soviet leader, he pulled his troops out of Afghanistan more than 20 years ago after a 10-year war.
UK Foreign Secretary William Hague said troops would not be withdrawn from the country until their "very difficult" work was complete.
In an interview with the BBC's Moscow correspondent Steve Rosenberg, Mr Gorbachev praised President Barack Obama for his decision to begin withdrawing troops next year, but said the US would struggle to get out of the situation.
"Victory is impossible in Afghanistan. Obama is right to pull the troops out. No matter how difficult it will be," Mr Gorbachev said.
He said before the Soviet Union withdrew from Afghani
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