WASHINGTON - With President Barack Obama lobbying Congress to agree to the United States' punishing Syria for alleged use of chemical weapons, he must persuade wary lawmakers that Syria's response won't lead to tit-for-tat retaliation that escalates the conflict.
Obama has repeatedly vowed a targeted attack won't seek to oust President Bashar al-Assad or aid the rebels. But the use of force often brings unintended consequences.
"Anyone who claims to have a crystal ball here doesn't," warned Paul R. Pillar, a former senior CIA official with responsibilities in the Middle East. "This does stir the pot in ways that increase the risk or chance of certain things happening, even though one can't place specific odds on it or make a specific prediction."
Pillar and other experts scoff at the notion of a surgical hit, noting that military forays into Iraq, Libya and Afghanistan have all brought consequences of a second and third order.
"This ought to remind people that it is very unlikely that anything we do in a limited way is going to be limited in the way we prefer,'' said Pillar, who now teaches at Georgetown University, in the nation's capital.
Obama was asked about the potential for escalation at a news conference Friday in the Russian city of St. Petersburg. He attempted to downplay the chances but seemed to be making the point that anything can happen.
"Is it possible that Assad doubles down in the face of our action and uses chemical weapons more widely? I suppose anything is possible, but it would not be wise," Obama said. "At that point, mobilizing the international community would be easier, not harder.''
Syria has many ways to respond to a U.S. attack. The Assad regime could strike back directly or through proxies, inside Syria and outside.
Assad's most immediate way to punish American attacks could be to retaliate in a way that drives up oil prices, squeezing the already soft U.S. and European economies.
As tensions with Syria rose two weeks ago, the price of U.S. crude oil soared past $112 a barrel before edging back to a range between $107 and $109 a barrel. Traders justify the high prices as a "security'' premium; U.S. oil remained above $107 a barrel at the end of trading Friday.
"What I'm concerned about is the retaliation to the retaliation. Mostly, we're concerned about it spilling over into attacks on Israel,'' said John Kilduff, an oil trader and partner in the hedge fund Again Capital.
Seeking to spike oil prices, Syria could strike at the pipeline in northern Iraq that connects with Turkey and the outside world.
"There are some real vulnerabilities on Syria's border that hang in the balance,'' said Kilduff, noting a sympathetic bomber in Saudi Arabia could send oil prices soaring. "Any kind of perceived threat to the (Saudi) royal family is just going to raise the security premium mightily.''
Much depends on how threatened the Assad regime feels. If a strike does little to threaten Assad, it emboldens him. If Assad is threatened, it raises the stakes for retaliation because the very existence of the regime would then be at stake.
"I think that some of these scenarios for 'unforeseen consequences' are a bit alarmist. I think the threats emanating from Damascus and Tehran are meant to unsettle nervous populations in western countries," said Wayne White, a scholar at the Middle East Institute and a former deputy director of the State Department's office in charge of Middle East intelligence.
By retaliating, Assad would invite even more foreign intervention in Syria's conflict, White said.
If there is a strike, both Assad and Obama must calibrate their responses with an eye toward an end goal. For Assad, it's a basic one: outlasting the insurgents and surviving. For Obama, the matter is more complicated.
"You do ultimately want a negotiated outcome to this conflict because we certainly don't want to see the regime win - but we don't want to see a straight-up victory for the opposition,'' said Michael Singh, a former top national security adviser during the administration of President George W. Bush.
A collapse of the Assad regime could leave parts of Syria ungovernable and strengthen jihadists who make up part of the opposition, he cautioned.