Opponents of Syrian President Bashar al-Assad claim he has used chemical weapons to kill his own citizens, and they have circulated a video showing bodies of some who are alleged to have died of chemical weapons poisoning.
President Obama warned that if it were proven, it would cross a "red line" for the United States.
"To use potential weapons of mass destruction on civilian populations crosses another line, and that is going to be a game-changer," the president said in March.
Last week, several U.S. officials, including Defense Secretary Chuck Hagel, agreed with British, French and Israeli intelligence sources who confirm that the Assad regime did use chemical weapons.
That prompted the following exchange at a White House press conference between ABC News correspondent Jonathan Karl and White House press secretary Jay Carney:
Karl: Jay, did the president mean it when he said use of chemical weapons are a game changer in Syria?
Carney: Yes, he did.
Karl: So what does that mean?
Carney: The president made clear that the use of or the transfer to terrorist groups of chemical weapons by the Assad regime would be a crossing a red line, and he retains all options to respond to that.
Karl: Including military force? Including military?
Carney: All options. All options.
As distasteful as Assad is to the United States, the Syrian opposition features a strong al Qaeda presence, a decided U.S. enemy.
Still, a growing number of lawmakers, including Sen. Lindsey Graham, R-S.C., say Washington may need to intervene to help take down Assad if for no other reason than to remind the world that the United States stands by its word.
"If we keep this hands-off approach to Syria, this indecisive action toward Syria, kind of not knowing what we're going to do next, we're going to have a war with Iran because Iran is going to take our inaction in Syria as meaning we're not serious about their nuclear weapons program," Graham warned on CBS "Face the Nation."
While Washington debates Syria policy, Israel is fortifying the Golan Heights along the Syrian border, a border that has been generally quiet since the last war 40 years ago.
The strengthening comes as former Israeli Defense Minister Benjamin Ben-Eliezer announced that Syria has begun to funnel chemical weapons to the Iranian-backed terror group Hezbollah in Lebanon.
On the Golan Heights, Israeli Brigadier-General Gal Hirsch said Israel must be prepared.
"We must be ready to be able to fight against radical fundamental activities that will come from Syria," he explained. "And that is what we are doing here."