In early October, New York lawyer Stanley Cohen found himself at the forefront of a private effort to negotiate the release of Islamic State captive Abdul-Rahman (Peter) Kassig, documented in a recent report by The Guardian. Cohen, whose past legal clients have included members of Hamas and Hezbollah, used his extensive contacts in the region to help arrange a promising dialogue between a prominent Jordan-based Salafi Islamist scholar and his counterpart in Islamic State.

Barely a month later, Kassig was dead at the hands of his captors — thanks to U.S. authorities who refused to intervene with a friendly government, Cohen now says.

Kassig, an ex-U.S. Army Ranger turned aid worker, was captured by the Islamic State in October 2013 while on a mission to deliver food and medical supplies to civilians in the Syrian city of Deir Ezzor. In a desperate effort to help secure the Iraq War veteran’s release, Palestinian friends of Kassig reached out to Cohen at the beginning of October in the hopes that he could help broker a negotiation to free Kassig.

While he lacked connections with Islamic State itself, Cohen was able to reach out to Jordan-based Islamist scholar Abu Muhammad al-Maqdisi, and convince him to open discussions with Turki Binali, a one-time protege of Maqdisi’s who had since turned radical and joined with I.S. The goal of the dialogue was to free Kassig and create an agreement that would preclude further executions of Western hostages at the hands of Islamic State. This, in turn, would be achieved by convincing Binali, one of the most prominent religious authorities within I.S., to officially forswear execution tactics. Maqdisi, a popular Salafi scholar who referred to Binali in discussions as “his ungrateful son”, was also perceived as being well-placed to achieve this goal.

While arranged by Cohen, the dialogue between the parties proceeded with the consent of FBI officials, whom Cohen says gave assurances regarding the safety of its participants.

The negotiations showed promise and succeeded in temporarily forestalling Kassig’s execution. But they ultimately faltered after Jordanian police suddenly arrested Maqdisi on October 27th on a charge of “incitement“, purportedly for an online blog post he had written before negotiations began that had characterized the bombing campaign against Islamic State as a “crusade”.

With the arrest of the main interlocutor seeking Kassig’s release, Cohen’s backchannel to Islamic State was severed. Kassig is believed to have been executed not long after, on November 16.

Speaking to The Intercept over the past week, Cohen alleged that the U.S. government prioritized political considerations over the well being of Kassig and other hostages and declined to take steps within its power to secure his safety.

“After the arrest of Maqdisi, it was easily within the power of U.S. government officials to call their counterparts in Jordan and ask for his release so that the negotiations could continue,” Cohen said. “By refusing to do so, the U.S. government all but guaranteed the murder of Kassig.”

In emails provided to The Intercept by Cohen, FBI agents assigned to the case expressed reticence about the prospect of an official intervention with Jordan to secure Maqdisi’s release. This, despite the knowledge that the negotiations being led by Maqdisi offered the only viable hope for a settlement which might secure Kassig’s safety.