Former Soviet leader Mikhail Gorbachev has said that NATO cannot win victory in Afghanistan.
In an interview with the BBC, Gorbachev said the US should pull out.
"What's the alternative - another Vietnam? Sending in half-a-million troops? That wouldn't work," he said.
As Soviet leader, Gorbachev took the decision to withdraw Soviet troops from Afghanistan.
The USSR's ill-fated invasion was finally decided to have failed in 1986, after a decade of troop losses the country to the US-assisted mujahideen.
"Victory is impossible in Afghanistan. Obama is right to pull the troops out. No matter how difficult it will be", Gorbachev said in the interview.
US campaign has 'failed' to pressure Taliban
The news came as the Washington Post cited US military and intelligence officials as saying the US military campaign against the Taliban has failed to destroy the group or pressure its leaders to seek peace. AFP reports.
The intense military campaign, including drone strikes and more commando attacks, has inflicted some temporary setbacks on the Afghan insurgency, the sources told the newspaper, speaking on condition of anonymity.
However US intelligence officials say that captured or killed Taliban commanders are often replaced in days, the insurgents seem content with small scale tactics of intimidation and assassination, and appear confident they can outlast the US troop buildup.
"The insurgency seems to be maintaining its resilience," an unnamed senior Defense Department official involved in war assessments told the Post.
Taliban 'reestablish and rejuvenate'
Taliban fighters have consistently shown that they can "reestablish and rejuvenate," sometimes just days after a defeat by US forces, the official said, according to AFP.
According to the Post, the assessments "are consistent across the main spy agencies responsible for analyzing the conflict, including the CIA and the Defense Intelligence Agency."
The joint CIA-military efforts to target Taliban leaders have caused senior operatives to move more often and increase security. But the impact on the Taliban's highest ranks has been limited, the Post said.
"For senior leadership, not much has changed," the defense official told the newspaper.
"At most we are seeing lines of support disrupted, but it's temporary. They're still setting strategic guidance" for operations against the US-led coalition forces in Afghanistan.
Taliban operatives have been focusing on President Barack Obama's stated intention to start withdrawing troops in mid-2011.
Taliban operatives, citing leader Mullah Mohammad Omar, tell one another, "The end is near," the officials told the Post.
