If it's assumed that a U.S. or allied attack on Syria is inevitable, then probably the least-bad outcome for oil markets would involve a punitive strike on Syrian military installations that then goes unanswered by Assad. Such a scenario would provide political cover to President Barack Obama, who warned this year that chemical attacks marked a line that the United States would not let Syria cross without facing retaliation.
"Less of a nightmare, and more probable, is that [the U.S.] lobs a few missiles and attacks a few military bases. And Obama says a line was crossed and I did what I said I would," Akacem said. "Then everybody goes home."
Another possibility is that Syrian allies act to stop the conflict from escalating. Perhaps counterintuitively, Iran or Russia could step up to help defuse the looming conflict or hold Assad back from retaliating, Haley said.
"It could be that both Iran and Russia come to the conclusion that it's becoming too high a cost to support Assad, especially if they want some sort of peaceful economic coexistence with the West," he said.
Haley noted that Iran in particular would like to get out from underneath Western economic sanctions that have crippled the country and devastated its middle class, which once was the largest in the Middle East. Speaking out against Syria's Assad could, in some small way at least, help the Islamic state mend economic ties with the rest of the world.
On Wednesday, Iran's new president, Hassan Rouhani, posted a message to Twitter saying he and other Iranian offiicals "completely and strongly condemn the use of chemical weapons" in Syria.
Russia, which has already found itself on the losing side, diplomatically and strategically, after Western clashes with Libya and Iraq, could use its influence on Syria to restrain that country and "actually take the lead and come out winning," Haley said.
On the other hand, Russia could also use Western strikes on Syria as a pretext for hiking the fuel prices it charges its Western customers in Europe. Russia is the largest supplier of oil, coal and natural gas to Europe.
Experts who spoke to CNBC disagreed about the likelihood of Iran or Russia acting to suppress a Syrian counterattack. But all indicated that the possible outcomes stemming from U.S.-led strikes are hugely varied and impossible to forecast.
"I think it's just too hard to call," Haley said.
—By CNBC's Ted Kemp and Yousef Gamal El-Din.