WATCH: Defense Secretary Calls For Faster Action Against ISIS

WASHINGTON — (CNN) U.S. Defense Secretary Ashton Carter says the death of a Navy SEAL in Iraq this week shows American troops are “at risk” as they fight ISIS in the region – but the risk is “necessary”.

Carter spoke exclusively to CNN’s Christiane Amanpour after Charles Keating IV died in combat Tuesday.

Keating was one of more than 4,000 U.S. servicemen in Iraq to advise local forces and conduct special operations against ISIS. He was killed when roughly 100 ISIS combatants launched what Carter described as “a surprise ISIS attack” on Peshmerga fighters some 18 miles north of Mosul.

“His death is tragic and it was a heroic action he was part of… but he was operating with one of the toughest forces in the whole Middle East – certainly in the Iraq-Syria theatre against ISIL – namely the Peshmerga from northern Iraq,” Carter said.

“In addition to being tragic, [his loss] shows us this is a risky campaign… Americans are at risk doing it, but it’s necessary. We need to, [and] we will defeat ISIL – but there’s going to be risk associated with it,” he said using the administration’s term for the terror group.

The Obama administration is sending increasing numbers of troops to Iraq and Syria to fight ISIS.

An initial contingent of 275 advisers were deployed in Iraq in 2014; now the official troop level is 4,087 — and the unofficial tally higher. In Syria, U.S. President Barack Obama plans to increase the number of American troops six-fold – from 50 to 300.

There are critics of this gradual deployment; Republican Senator John McCain, Chairman of the Senate Armed Services Committee, accuses the Obama administration of “grudging incrementalism”.

Amanpour put this to Carter.

“We do want to get this over with soon, and that means accelerating what we’re doing,” he said. “Any war proceeds step by step but we need to take these steps as aggressively and quickly as possible.”

“I too am impatient. I want to accelerate this,” he added.

“[But] my experience with the Chairman [of the Joint Chiefs of Staff] has been that when we go to the President with something that we know will accelerate the progress there he has approved those things – and that has been true in both Iraq and Syria.”

Carter was speaking at the U.S. European Command headquarters in Stuttgart, Germany, where he hosted a meeting of defense ministers from countries at the forefront of the anti-ISIS coalition Wednesday morning.