Kerry also urged lawmakers not to try to limit where the fighting occurs, or to define too narrowly the Islamic State-affiliated groups that U.S. forces can attack as part of the mission.
Any new congressional rules should give President Obama "a clear mandate, and the flexibility he needs," Kerry said in an appearance before the Senate Foreign Relations Committee.
Kerry and the lawmakers were having their first face-to-face encounter over Congress' desire to legislate an authorization for the use of military force that would provide a legal basis for fighting Islamic State.
Obama has repeatedly ruled out the use of U.S. ground forces in Syria and Iraq, saying that local troops can provide the ground capabilities to complement U.S. airstrikes. But Kerry argued that any legal authorization should be broad, to allow field commanders to adjust to any unforeseen circumstances.
Setting geographic limitations could become an unwelcome restriction if, for example, the militant group began to move into Libya, Kerry said.
He said the administration could accept a three-year limit on the campaign, as proposed in legislation offered by committee Chairman Sen. Robert Menendez (D-N.J.). But Kerry said the language should allow the administration to extend the campaign beyond three years if necessary, subject to consultation with Congress.
The Obama administration has been relying on authorizations for military action that were provided by Congress in 2001 and 2002, after the Sept. 11, 2001, attacks on the United States.
The administration and Congress have been eager to write a new legal foundation for the military campaign, which is expected to last years.
But the subject is politically perilous. Some liberal lawmakers are worried about an open-ended conflict, while conservatives want to give the commander in chief wide latitude but are skeptical about Obama's approach to Islamic State.
Kerry said he saw Menendez's proposal as the basis for negotiations with lawmakers over the coming weeks, and suggested that with a few changes the proposal could be made acceptable to both sides.
He said he was open to language that would describe how troops should be used. But "it does not mean we should preemptively bind the hands of the commander in chief or our commanders in the field in responding to scenarios and contingencies that are impossible to foresee," he said.
Kerry said the administration would like to reach a bipartisan agreement on a bill, because that would send the best signal to U.S. allies in the region and to Islamic State.
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