A general view of damaged buildings is seen in the rebel-held area of Douma, Syria as a sandstorm blows over the city on September 7, 2015
Washington (AFP) - Former CIA chief David Petraeus said Tuesday that the United States should play a more active role in Syria, including setting up safe havens and implementing no-fly zones to prevent regime planes dropping barrel bombs.
The retired four-star general, who became a household name in America after overseeing the troop "surge" in Iraq in 2007, also gave an emotional apology for sharing classified information with his mistress in a scandal that led to his resignation from the Central Intelligence Agency.
Speaking before the Senate Armed Services Committee as an expert on US policy in the Middle East, Petraeus said the US-led coalition fighting the Islamic State group had made "inadequate" progress in Iraq and Syria, and called the Syrian civil war a "geopolitical Chernobyl."
"The fallout from the meltdown of Syria threatens to be with us for decades," he said. "The longer it is permitted to continue, the more severe the damage will be."
He said Washington had the capability to stop Syrian President Bashar al-Assad's planes dropping bombs over civilian populations.
"There are actions the US and only the US can take that would make a difference. We could, for example, tell Assad that the use of barrel bombs must end. And that if they continue, we will stop the Syrian air force from flying. We have that capability," Petraeus said.
"This would not end the humanitarian crisis in Syria... it would remove a particularly vicious weapon from Assad's arsenal."
Petraeus's comments came just days after lawmakers on the same committee blasted America's strategy against the Islamic State group in Iraq and Syria.
In Iraq, Petraeus described a see-sawing battlefront in which IS fighters lose ground in some areas only to gain it elsewhere.
He said the US needs to boost support for Iraqi security forces, as well as the Kurdish peshmerga and Sunni tribal forces. One way to do this, he said, would be to introduce controllers into those groups who would be able to call in coalition airstrikes.
- 'Serious mistake' -
Petraeus highlighted the dilemma the West faces over Assad. While America and its allies do not want him in power in the long run, they don't want his ouster without knowing who or what would replace him.
"He has to go ultimately, but the key word there is 'ultimately,'" Petraeus said.
"Until we have a sense of what will replace him, we need to be very careful not to push him out because what comes after could actually be even worse."
Petraeus said he supports the creation of secure enclaves in Syria to protect the battered civilian population in a conflict that has claimed nearly 250,000 lives.
"I would also support the stability of enclaves in Syria protected by air power, where a moderate Sunni force could be supported and where additional forces could be trained.
"Internally displaced persons could find refuge and the Syrian opposition could organize."
He prefaced his comments with an emotional apology for actions that led to his dramatic fall from grace.
"Four years ago, I made a serious mistake, one that brought discredit on me and pain to those closest to me," he said.
"There's nothing I can do to undo what I did. I can only say, again, how sorry I am."
Petraeus, who led the US wars in Iraq and Afghanistan, fell from grace earlier this year when he was given two years' probation and fined $100,000 for providing classified information to his mistress and biographer Paula Broadwell.
US leaders praised his efforts during the surge and credited him for salvaging the troubled war effort.
He resigned from the CIA in 2012, after serving just 14 months at the helm of the spy agency.