Washington — Secretary of State John Kerry and top defense leaders made the case before the Senate Foreign Relations Committee Wednesday for President Barack Obama’s request to Congress to use military force against the self-proclaimed Islamic State.

“We simply can’t allow this group of murderers and thugs to achieve their goal,” Kerry said.

The request made last month is somewhat symbolic since the president, as commander in chief, already has authority to engage ISIS. The administration wants Congress’ approval to demonstrate unity and boost troop morale, said Kerry, who during his time in the Senate chaired the Foreign Relations panel.

The use-of-force resolution would last three years and allow the U.S. military to target ISIS, as well as its allies who threaten Americans, without geographical restrictions. It does not authorize a long term, large-scale ground offensive as seen previously in Iraq and Afghanistan, said Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff.

“This authorization is suitable to the campaign as we have presently designed it,” Dempsey said. “We expect our enemy will continue to adapt their tactics and we will adapt ours.”

The terrorist group known as ISIS controls large portions of Syria and Iraq and gained international notoriety through beheadings and mass killings.

At the hearing, Republican senators’ main concerns over giving authority to the president pertained to Iran.

“I believe much of our strategy with regards to ISIS is out of a desire not to upset Iran, so they don’t walk away from the negotiating table,” Sen. Marco Rubio, R-Fla., told Kerry.

Kerry said Rubio’s statement completely contradicted the facts of the situation, but added that he was not at liberty to discuss details of the nuclear capability negotiations with Iran.

Senator Bob Corker, R-Tenn., chairman of the committee, raised concerns over whether Iranian-supported Shia militia in Iraq could turn on U.S. troops. Dempsey said that the scenario was unlikely and that any regional support fighting ISIS, even from the Iranians, would probably be a “good thing” militarily.

Democratic senators such as Bob Menendez, D-N.J, ranking member of the committee, were more concerned with the scope of the authorization.

“We are not willing to give this, or any other president, an open authorization or a blank check,” Menendez said.

The resolution awaits approval from the committee before heading to the full Senate for a vote.