WASHINGTON (CBSDC/AP) — Vice President Joe Biden says the United States will follow the Islamic State of Iraq and Syria terror group to the “gates of hell.”

Speaking in Portsmouth, New Hampshire, following Tuesday’s video release of the beheading of American journalist Steven Sotloff, Biden minced no words on how the U.S. will respond.

“We will follow them to the gates of hell until they are brought to justice because hell is where they will reside,” Biden said.

The vice president added: “If they think the American people will be intimidated, they don’t know us very well.”

During a press conference in Estonia on Wednesday, President Barack Obama said that the United States will not be intimidated by ISIS and that a coalition will be built to “degrade and destroy” the group.

Obama still did not give a timeline for deciding on a strategy to go after the extremist group’s operations in Syria. “It’s going to take time for us to be able to roll them back,” the president said at a news conference during a visit to Europe.

The president’s comments came after he said the United States had verified the authenticity of a video released Tuesday showing the beheading of Sotloff, two weeks after journalist James Foley was similarly killed.

Obama vowed the U.S. would not forget the “terrible crime against these two fine young men.”

“We will not be intimidated. Their horrific acts only unite us as a country and stiffen our resolve to take the fight against these terrorists,” Obama said. “And those who make the mistake of harming Americans will learn that we will not forget, and that our reach is long and that justice will be served.”

Separately, Secretary of State John Kerry said in a statement: “Barbarity, sadly, isn’t new to our world. Neither is evil.”

“We’ve taken the fight to it before, and we’re taking the fight to it today,” Kerry said. “When terrorists anywhere around the world have murdered our citizens, the United States held them accountable, no matter how long it took. And those who have murdered James Foley and Steven Sotloff in Syria should know that the United States will hold them accountable too, no matter how long it takes.”

Obama also sought to clean up the damage from his statement last week that “we don’t have a strategy yet” for dealing with the Islamic State group in Syria. Republicans quickly seized on the remark to argue the president lacks a coherent approach to fighting the extremist group.

“It is very important from my perspective that when we send our pilots in to do a job, that we know that this is a mission that’s going to work, that we’re very clear on what our objectives are, what our targets are,” Obamasaid. “We’ve made the case to Congress and we’ve made the case to the American people, and we’ve got allies behind us so that it’s not just a one-off, but it’s something that over time is going to be effective.”

In the Sotloff video, a masked militant warns Obama that as long as U.S. airstrikes against the militant group continue, “our knife will continue to strike the necks of your people.”

“I’m back, Obama, and I’m back because of your arrogant foreign policy towards the Islamic State, because of your insistence on continuing your bombings … and on Mosul Dam, despite our serious warnings,” the executioner said. “You, Obama, have but to gain from your actions but another American citizen. So just as your missiles continue to strike our people, our knife will continue to strike the necks of your people.”

Obama responded that the airstrikes have been effective in blunting the militant threat and he will continue to battle the “barbaric and ultimately empty vision” that the Islamic State represents. He said he will be consulting with NATO allies at a summit in Wales Thursday and Friday on a strategy to combat the Islamic State and other militant networks that arise.

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