Biden's warning to ISIS militants: 'We will follow them to the gates of hell'

Photo by Joe Raedle/Getty Images

(CNN) -- Vice President Joe Biden on Wednesday issued a sharp warning to ISIS militants, saying after the United States is done grieving the death of two American journalists, their killers will have to answer for their actions.

"They should know we will follow them to the gates of hell until they are brought to justice," he forcefully told an audience at an event on the New Hampshire-Maine border. "Because hell is where they will reside. Hell is where they will reside."

Biden opened his remarks in memory of Steven Sotloff, the journalist who was beheaded by ISIS militants Tuesday, two weeks after Jim Foley was executed in the same horrific manner on video. Foley was from New Hampshire, while Sotloff lived there for boarding school.

Describing the perpetrators as "barbarians," Biden vowed that Americans would not be frightened or intimidated by the heinous acts.

"We came back after 9/11. We dusted ourselves off and we made sure that Osama bin Laden would never, ever again threaten the American people," Biden said. "We came back Boston strong, blaming no one but resolve to be certain that this didn't happen again."

"As a nation, we're united, and when people harm Americans, we don't retreat," he later said. "We don't forget."

The vice president, who's mulling a 2016 presidential bid, made his remarks at the Portsmouth Naval Yard in a speech about the economy. He was accompanied on stage by U.S. Sen. Jeanne Shaheen, a New Hampshire Democrat who's running for re-election this year.

After Sotloff's killing, President Barack Obama faced a chorus of bipartisan calls from Congress to act more aggressively and come up with a concrete strategy to combat ISIS, beyond the already ongoing targeted air strikes.

In Europe this week for the NATO summit, the President took a similar line as Biden earlier Wednesday, saying the U.S. "will not be intimidated" by the killers.

"Those who make the mistake of harming Americans will learn that we will not forget ... that our reach is long and that justice will be served," Obama said.