As the United States conducts airstrikes in Iraq against the Islamic State, some foreign policy experts are calling on the White House to align with Syrian President Bashar Assad to help defeat the Sunni extremists who have seized territory in Syria and killed thousands in the region. But such an alliance would be complicated -- Assad is a dictator whose use of chemical weapons against his own people almost pushed the U.S. into direct military conflict with him in recent years.

Any deal with Assad against the Islamic State, also known as ISIS, may have to be done privately because of how he’s treated his own people, according to Steven Walt, professor of international affairs at Harvard’s Kennedy School of Government.

“If ISIS continues to be a problem, or if it gains more ground in Syria, I can imagine the United States quietly reducing its support for Assad’s other rivals so that the regime can focus more on thwarting the jihadi threat,” Walt told BuzzFeed. “But Assad’s own conduct and the administration’s past rhetoric would make it very hard to embrace his government publicly, even as the lesser of several evils.”

Nevertheless, foreign intelligence experts are urging the U.S. to embrace the axiom, “The enemy of my enemy is my friend."

Nada Bakos, a former intelligence analyst, said on Twitter that a U.S. deal with Assad would need to include an agreement that the Syrian president stop killing his own people. Bakos isn’t proposing an explicit partnership with Assad, but she argued the U.S. should stop arming some of the rebels trying to topple his regime so Syria can focus on attacking ISIS, which controls portions of eastern Syria that along with territory it seized in Iraq was used to form a caliphate. 

“I don’t believe Assad’s forces can achieve that singlehandedly and we aren’t about to partner with him, nor should we,” Bakos told BuzzFeed. “However, arming the rebels at this point just means a longer, protracted war that is already full of proxies. It would be almost endless. If we can identify why we are taking action, we can then decide on our best course of action (which is likely still pretty awful). Our goal should be to stop the chaos, but sometimes all we can do from the outside is just help contain it.”

Last year, British Prime Minister David Cameron pushed for airstrikes against Assad after it was revealed the Syrian president used chemical weapons. Now, British military leaders are calling for airstrikes in Syria not against Assad but ISIS.

"The old saying 'my enemy's enemy is my friend' has begun to have some resonance with our relationship with Iran. I think it's going to have to have some resonance with our relationship with Assad,” Gen. Lord Dannatt, the former chief of general staff for Britain’s army, told BBC Radio 4, according to the Telegraph. "I think whether it is above the counter or below the counter, a conversation has got to be held with him. Because if there is going to be any question of airstrikes over Syria airspace, it's got to be with the Assad regime's approval."