Palestinian Authority President Mahmoud Abbas shakes hands with U.S. President Barack Obama, on March 17, 2014. Photo: Screenshot.

A lead negotiator for the Palestinian Authority in the ongoing U.S.-brokered peace talks with Israel on Tuesday threatened to resume a unilateral push for international legitimacy at the United Nations if the fourth and final agreed upon round of prisoners are not released, Egypt’s Al Ahram daily reported, citing the Associated Press.

Nabil Shaath said that if the prisoner release is called off, the Palestinians will “immediately” turn to the UN. According to reports, Israel is pushing for an agreement to extend the current round of talks beyond the April deadline, imposed by the U.S., and views the prisoner release as a carrot for advancing the talks rather than an end-goal.

At the start of the talks, in July, the government of Israeli Prime Minister Benjamin Netanyahu pledged to release 104 prisoners, many of them convicted murderers and terrorists, in four stages as the talks progressed, with the final tranche to be released by March 29.

The prisoner releases have been very controversial in Israel, where Netanyahu was deeply criticized by members of his governing coalition and the families of the victims, for whom the murders of their loved ones remain open wounds.

Almagor, an NGO that advocates for victims of terrorism, has petitioned Israel’s High Court of Justice, demanding that it stop the government from releasing the prisoners, and held demonstrations carrying banners that read “Shame on You!“