US lawmakers Tuesday called for Secretary of State John Kerry to present administration policy for "rolling back" the Islamic State's gains, after the rampaging group claimed it beheaded a second American.

With members of the House and Senate warning that President Barack Obama has not done enough to combat the extremist group, House Foreign Affairs Committee chairman Ed Royce said he was summoning Kerry to testify once Congress returns next week from its recess.

"Everyone agrees that the administration needs a strategy, that the president has to explain to the American people and explain to Congress how we are going to meet this threat," the Republican Royce told reporters on a phone call from Israel, where he was on a congressional mission.

He said he expected Kerry to present a plan for "rolling back ISIS," another name to describe the extremist group that on Tuesday released a video purporting to show the beheading of American journalist Steven Sotloff.

The committee's top Democrat, Eliot Engel, said lawmakers were "horrified" by the apparent murder.

Obama is operating under the war powers resolution, which provides the president with power to authorize US military action without congressional consent, to launch air strikes on Iraq beginning last month.

It requires Obama to seek congressional approval if the actions extend beyond 60 days, something both Royce and Engel believe Obama will do.

"We anticipate there would be a vote for authorization of the use of force" before the 60-day period expires, Royce said.

On Sunday, Senate Intelligence Committee chair Dianne Feinstein warned that Obama was not doing enough to tackle the IS threat.

"I think I've learned one thing about this president, and that is he's very cautious. Maybe in this instance, too cautious," Feinstein told NBC's "Meet the Press." (AFP)