If Syria were to fall into complete chaos and if the chemical weapons of President Bashar al-Assad’s government there were at risk of falling into the hands of a militant group like Al Nusra, Mr. Kerry said, “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.”

Later, under questioning by Senator Bob Corker of Tennessee, the ranking Republican, Mr. Kerry walked back his comment, insisting that he had only been speaking about a hypothetical case. “Let’s shut that door now as tight as we can,” Mr. Kerry said, without quite doing so. “There will not be American boots on the ground with respect to the civil war.”

The Senate resolution — released on Tuesday night by Mr. Corker and the committee’s chairman, Robert Menendez, Democrat of New Jersey — would limit the president’s options and prohibit the use of ground forces. Any strike, it says, should be “tailored” to only deter Syria from using chemical weapons again and to cripple its capacity to do so.

The resolution would prohibit “boots on the ground” and require “the Obama administration to submit their broader plan for Syria,” Mr. Corker said in a statement.

Mr. Menendez added, “We have an obligation to act.”

In one of the most heated moments of the hearing earlier, Senator Rand Paul, the Kentucky Republican, said that Mr. Obama might go through with an attack if Congress failed to authorize it. Mr. Kerry said that he did not know what Mr. Obama would decide but that the president had the authority to do so under the Constitution.

It was a vivid tableau: Mr. Kerry — the former senator and chairman of the Senate Foreign Relations Committee, who voted to authorize the Iraq war in 2003, then turned against it — imploring his ex-colleagues to authorize an act of war.