U.S. Vice President Joe Biden Wednesday warned Islamic State militants who executed James Foley and Steven Sotloff that the U.S. would not stop until they were brought to justice and punished for their crimes.

In one of the strongest remarks so far about the executions to come out of the Obama administration, Biden called the Islamic State militants "barbarians" and vowed that America "will follow them to the gates of hell."

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"We don't forget," Biden said. "We take care of those who are grieving, and when that's finished, they should know we will follow them to the gates of hell until they are brought to justice, because hell is where they will reside."

The vice president was speaking on economics at the Portsmouth Naval Yard in New Hampshire.  The audience met his comments with resounding applause as he declared that the American people will respond to the killings the way they did after the Sept. 11, 2001 attacks and the Boston Marathon bombings.

After he opened about America's reaction to the executions, Biden, flanked by Democratic members of Congress, spoke about the importance of the middle class, which he called the backbone of the U.S. economy.

"The reason why America has been the most stable nation in the world is because we've had an ever-growing middle class where people believe that if they play by the rules they get a shot," Biden said.

The vice president's speech was the latest of several appearances in states that hold early presidential primaries. Biden was widely believed to be eyeing another presidential bid in 2016. He has sought the presidency twice in the past.

Meanwhile, New Hampshire Republicans criticized the visit. Sen. Kelly Ayotte, a prominent member of the Republican caucus, was not at the shipyard. RNC spokesman Michael Short said it was clear the vice president was "more interested in buoying his presidential ambitions and the reelection prospects of vulnerable Democrats."

Short said Biden has injected politics into an event where national security and economic issues should be the focus.

TagsISIS, Iraq, Biden, Obama, presidential politics