Secretary of State John Kerry told a panel of senators that he couldn’t absolutely rule out the use of U.S. combat troops in Syria if groups hostile to the United States seized any of Syria’s chemical weapons.

Lawmakers' concerns that America would be drawn into a broader conflict – already evident among many members of the Senate – deepened when Kerry speculated openly at a hearing Tuesday about the circumstances under which the U.S. might deploy combat troops in Syria.

President Obama called for a military strike on President Bashar Assad's regime in retaliation for its use of chemical weapons against its own citizens and asked Congress to authorize it. But Obama had promised that the intervention would be limited and would not include U.S. troops.

But Kerry said ground troops could be necessary to ensure stability if Syria “imploded” or there was “a threat of Syria’s chemical weapons cache falling into the hands” of terrorist groups.

“I don't want to take off the table an option that might or might not be available to a president of the United States to secure our country,” Kerry said.

But the Secretary of State, realizing the concerns that senators had with his remarks, moved quickly to "shut the door as tight as we can” against the use of combat forces in Syria's civil war.

“All I did was raise a hypothetical possibility, and I’m thinking out loud,” he said, assuring senators that “there will not be American boots on the ground with respect to the civil war.”

A number of senators repeatedly cited their doubts about being drawn into a broader conflict, questioning Kerry about how to avoid such an eventuality.

“I don’t think there are any of us that are willing to support the possibility of having combat troops, boots on the ground,” Sen. Bob Corker, R-Tenn., said. Added Sen. Tom Udall, D-N.M., “I see this potential bombing campaign as a potential next step towards full-fledged war.”

Senate Foreign Relations Committee Chairman Bob Menendez, D-N.J., said his committee is working on the wording of a congressional resolution that could be finished as soon as Wednesday.

Sen. Ben Cardin, D-Md., said that the authorization of military force requested by the White House was far broader than lawmakers had expected. Cardin called on Congress to vote on “a resolution that is as tight as we can make it.”

While most senators talked about how to limit U.S. involvement, Sen. Ron Johnson, R-Wis., asked top administration officials why Obama wasn't going for "some kind of knockout punch" that would dethrone Assad.

"The reason is the president is listening to the American people and has made a policy decision that this is not something the United States of America needs to engage in," Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey said. "Is the Congress of the United States ready to pay for 30 days or 30,000 air strikes, and is there a legal justification for doing that?"

A Washington Post-ABC poll released Tuesday shows that 59 percent of Americans oppose military strikes against the Syrian government. Just 36 percent support it.

Despite this poll and others showing similar levels of opposition to a military strike, Sen. Rand Paul, R-Ky., said that it was “unlikely” that Congress would reject the president’s request for authorization.