President Barack Obama said Wednesday that the killers of two American journalists will be brought to justice, and their barbaric acts will do nothing to intimidate the United States.

Terror group ISIS released a video Tuesday showing the apparent beheading of journalist Steven Sotloff. A day later, U.S. officials said the video is authentic.

The killing is the second beheading of an American journalist in two weeks, and the militant group said it's a result of Obama's decision to conduct airstrikes against ISIS in Iraq.

Sotloff was also an Israeli citizen, a spokesman for the Israeli Ministry of Foreign Affairs said Wednesday.

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In the video, Sotloff kneels in the desert, dressed in an orange prison-style jumpsuit. A masked "executioner" lords over him, wielding a knife.

The journalist speaks; the executioner speaks. Then the victim is beheaded. The video is similar to one released two weeks ago showing the death of another American journalist, James Foley.

In the video released Tuesday, a British hostage is shown after the beheading of Sotloff, just as Sotloff was shown in Foley's video.

Obama said the United States "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," the President said.

Obama: ISIS killers will not intimidate U.S.

By Faith Karimi and Carol Jordan, CNN

He addressed his much-criticized statement last week that he has no strategy on ISIS. He said he was referring to a military strategy in Syria that "might" require congressional approval.

"Our objective is clear. That is to degrade and destroy (ISIS) so it's no longer a threat," he said. "We can accomplish that. It's going to take some time, it's going to take some effort."

ISIS, or the Islamic State in Iraq and Syria, refers to itself as the "Islamic State."

Obama said the world needs a regional strategy to defeat the group.

"We've been putting together a strategy that was designed to do a number of things. ... What we have to make sure is we have a regional strategy in place," he said.

In addition to the Americans' deaths, the British hostage showed at the end of the latest video appears to be in danger.

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British rescue attempt

The UK said it attempted to rescue its citizen "some time ago" but failed.

UK Foreign Secretary Philip Hammond provided scant details of the rescue attempt or any other plans in the works.

"You wouldn't expect me to discuss various options that we will be considering," he said. "But I can assure you that we will look at every possible option to protect this person."

Britain echoed the same sentiment as Obama.

"This country will never give into terrorism ... a country like ours will not be cowed by these barbaric killers," UK Prime Minister David Cameron said.

"Our thoughts are with the British hostage and his family," Cameron said Wednesday in the House of Commons.