Wide gaps make a peace deal between Israel and the Palestinians impossible, former Palestinian negotiator Mohammed Ishtayeh said Wednesday, hours ahead of US Secretary of State John Kerry’s arrival in Israel for yet another round of talks aimed at moving negotiations forward.

Ishtayeh, a senior aide to Palestinian Authority President Mahmoud Abbas who quit the Palestinian negotiating team a month ago over Israeli settlement construction, said he believed US mediation was “unbalanced” in favor of Israel.

While noting that he was expressing his personal views, Ishtayeh urged other world powers to join the talks as Kerry prepared to return to the region Wednesday to try to salvage the troubled negotiations.

Kerry, slated to land Wednesday night, is expected to bring with him a US plan for security arrangements the West Bank.

However, ahead of the US envoy’s visit, Ishtayeh said that his sense is that Israel wants to annex large parts of the West Bank, one of the territories the Palestinians want for their future state.

Major differences “block any possibility of a peace deal,” he said.

Ishtayeh and chief Palestinian negotiator Saeb Erekat tendered their resignations to Abbas on October 31 following Israel’s announcement that it intended to demolish 20 Arab-owned buildings in East Jerusalem.

Abbas refused to accept the resignation letters. Since those letters were submitted a month ago, several rounds of talks have been held, including one last week.

Despite having officially resigned, Erekat said he would see the current round of negotiations through, whereas Ishtayeh insisted on his resignation.

On Wednesday, Erekat urged Kerry to salvage the faltering peace talks.

“Mr. Kerry must work to save the talks, to work to stop the deterioration of the talks caused by Israel’s continuing settlement activity and crimes committed in cold blood,” he told Palestinian radio, according to Reuters.

Under heavy US pressure, peace talks between Israel and the Palestinians resumed in July after a three-year hiatus. Although they have continued out of the media spotlight, reports have mounted that the two sides have reached an impasse.

Last month, Israel’s Housing Ministry published tenders for the planning of some 20,000 settlement units — an unprecedented number — including 1,200 homes in the controversial E1 corridor linking Jerusalem with Ma’aleh Adumim to the east, drawing harsh responses from the US and Palestinian Authority.

Netanyahu heeded the criticism and ordered the plan pulled back, saying the move to push forward tens of thousands of new units over the Green Line was a “meaningless step” that would create pointless tension with the international community.

Kerry’s visit will be his first to the region since the US was party to a nuclear deal singed with Iran which Israel had vociferously opposed, ramping up tensions between the two allies.