A U.S. missile strike on Syria could trigger an explosive chain reaction involving from Syria or its allies like Hezbollah and Iran, and the blowback could hit U.S. targets or Israel, experts told ABCNews.com.
Or Syria might simply stop using chemical weapons and there is no retaliation at all.
Gauging the ripple effect of a U.S. strike on Syria is part of the calculations of the Obama administration, but it is an imprecise science.
"When you do a military strike it often has ramifications you don't anticipate," said Dan Byman, a senior fellow of foreign policy at Brookings Institute.
Here are five scenarios the the U.S. could face in coming weeks.
1. Syria Will Try to Retaliate
Syria has already made bold threats toward the U.S. and its allies, specifically Israel, about retaliation for any U.S. intervention in Syria's civil war.
"If Damascus comes under attack, Tel Aviv will be targeted and a full-scale war against Syria will actually issue a licence for attacking Israel," Iran's Fars News Agency quoted a Syrian military official as saying. "If Syria is attacked, Israel will also be set on fire and such an attack will, in turn, engage Syria's neighbors."
|"We face major uncertainties regardless of what we do."|
But U.S. policy experts say it is unlikely that Assad's military forces have the capabilities to launch another large-scale attack at this point, given how committed their troops already are fighting the rebels within Syria. Any retaliation by Assad's military will largely be small-scale and symbolic, aimed at generating headlines and support rather than hurting U.S. allies or targets, according to Anthony Cordesman, an analyst at the Center for Strategic and International Studies.
"Syria can have a token form of escalation, although it's essentially committed almost all of the power it has (to the civil war)," Cordesman said. "If they did do something large-scale, their reprisal risk could outweigh their gains. In a world where every rocket is massive in terms of media reporting, they could do low level stuff to get a lot of propaganda gains, and do a lot of that without provoking response (from the U.S.)."
2. Iran Will Take Aim at Israel
Iranian leaders also issued strong rhetoric in recent days, warning the U.S. to stay out of the conflict in Syria and threatening to retaliate against Israel in response to any military meddling. One official was quoted in Iran's Fars news service saying that Iran would "flatten the place (Israel) that is tied to the U.S.'s national security."
But if Iran launched an attack on Israel, Cordesman said it is unlikely that the U.S. would come to its ally's defense.
"Iran could try to demonstrate its power by either using elements of the Al Quds Force or sponsoring a third party attack on anything from U.S. targets to Israeli targets to Jordanian targets," Cordesman said. "Israel will probably manage it own defense. We have strong reason not to get too involved at a time when we are working with so many Arab states," he said.
If Iran opts not to strike Israel or Jordan, it could still bolster its support for Assad, according to Byman.
"Iran and Russia might step up their response, sending more fighters, encouraging more fighters from Iraq and Lebanon, sending more arms, and using more diplomatic pressure," Byman said.