The Islamic State of Iraq and the Levant's (ISIS) execution of Steven Stoloff only proved they never intended to negotiate with the U.S. or its allies.

ISIS threatened to kill Sotloff two weeks ago, but said they would release their other prisoners if U.S. President Barack Obama would halt the air strikes against them.

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However, the release of the video on Tuesday wiped out hopes that the militant group was willing to negotiate for the lives of their captives, Foreign Policy reported.

Some U.S. intelligence officials think the ISIS may have killed Sotloff on the same day that they executed James Foley, the American journalist they purportedly beheaded in the first video they sent. If the hunch of the officials are correct, then the ISIS was never interested in setting the journalist free or bargaining for his release.

Before the release of the video, an unnamed U.S. defense official said ISIS had the capability to make it look like they recorded the Sotloff footage after they murdered Foley. The video reportedly did not indicate when the group killed Sotloff.

The speaker in the video mentioned the strikes on Iraq's Mosul Dam on August 17, two days before Foley's execution video was posted. The latter may have been beheaded on August 15 and this could mean that Sotloff's execution was not a response to the August 17 strikes, according to U.S. officials.

Sotloff wrote for Time, Foreign Policy and the Christian Science Monitor, and several other media firms. He disappeared in Syria in August last year, nine months after Foley was abducted.

Washington took ISIS' outrageous demands to mean that the group had no intention to free the two journalists. The militant group previously demanded a ransom of US$130 million in exchange for Foley's freedom and his editor at the GlobalPost said no one took that amount seriously.

ISIS also told the U.S. to release suspected Al Qaeda member Aafia Siddiqui, but Washington did not comply with that demand because it has a policy against negotiating with terrorist groups. Siddiqui is serving an 86-year jail sentence in Texas for attempting to kill American officials in Afghanistan.

Last week, Sotloff's mother released a video begging the ISIS to free her son, but the Islamist group ignored the plea. The group may have been trying to turn American citizens against Obama's anti-IS campaign.

The latest video showed the British-sounding executioner blaming Obama's foreign policy for Sotloff's death. Officials have yet to confirm the identity of Foley's murderer.

The video ended with the killer threatening to murder another prisoner he identified as David Cawthorne Haines, a U.K. citizen. If the video is confirmed as authentic, it would indicate that the ISIS is expanding its terrorist campaign to include British citizens.

Meanwhile, U.K. Prime Minister David Cameron is still considering joining the U.S. campaign against the IS.

TagsSteven Sotloff, Barack Obama, Foreign Policy, james foley, Mosul Dam, Iraq, Christian Science Monitor, U.S., U.K., david cameron, GlobalPost, Al-qaeda, Aafia Siddiqui, Afghanistan, David Cawthorne Haines