President Obama has ordered more troops to Iraq to protect U.S. diplomatic posts and workers in Baghdad after the gruesome beheading of another American journalist by the Islamic State.
The military personnel will offer protection as the country fights a growing insurgency from the ruthless jihadist army.
Obama condemned the killing during a news conference in Estonia early Wednesday morning.
"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," the president said.
"The bottom line is this: Our objective is clear and that is to degrade and destroy [Islamic State] so that it's no longer a threat not just to Iraq but also the region and to the United States," Obama continued.
For months, ISIS has been mounting attacks and capturing territory across Iraq and along the Iraq-Syria border, even in the face of American airstrikes.
Meanwhile, U.S. authorities have confirmed that footage released by ISIS Tuesday showing the beheading of U.S. journalist Steven Sotloff is authentic.
"Overnight, our government confirmed that, tragically, Steven was taken from us in a horrific act of violence," the president said.
The grizzly video is called "A Second Message to America" and shows the 31-year-old American on his knees in an orange jumpsuit before an Islamic State fighter.
"I'm back, Obama, and I'm back because of your arrogant foreign policy toward the Islamic State," Sotloff's executioner says in the video. "Just as your missiles continue to strike our people, our knife will continue to strike the necks of your people."
Sotloff's death comes two weeks after American journalist James Foley was executed in a similar video.
Investigators are trying to determine if the same hooded jihadist with an apparent British accent killed both journalists.
An Israeli official confirmed that Sotloff, who once attended the University of Central Florida in Orlando, also was an Israeli citizen.
Meanwhile, British Prime Minister David Cameron has taken the lead in responding to the Islamic State threat. He recently introduced legislation to stop ISIS fighters from returning to the United Kingdom.
"It is abhorrent that people who declare their allegiance elsewhere are able to return to the United Kingdom and pose a threat to our national security," Cameron said.
Obama's critics say his weak foreign policy is contributing to the terror group's rise. Both Democrats and Republicans are pushing the president to act quickly against ISIS.
"We have to deal with this threat comprehensively and thoroughly now, and that is what I want to hear and see from our commander in chief," Rep. Paul Ryan, R-Wis., said.
"I would say, I wish our president were showing the same leadership that David Cameron showed. What is President Obama waiting for?" Rep. Peter King, R-N.Y., asked.
Meanwhile, ISIS is holding at least one more British journalist and two American aid workers hostage.