Key mediator Egypt expressed skepticism Wednesday about the proposal meant to bridge gaps in cease-fire talks between Israel and Hamas as more details emerged a day before negotiations were expected to resume in Cairo.

Diplomatic efforts have redoubled as fears grow of a wider regional war after the recent targeted killings of leaders of the militant Hamas and Hezbollah groups, both blamed on Israel, and threats of retaliation.

“The Americans are offering promises, not guarantees,” the official said. “Hamas won’t accept this, because it virtually means Hamas will release the civilian hostages in return for a six-week pause of fighting with no guarantees for a negotiated permanent cease-fire.”

He also said the proposal doesn’t clearly say Israel will withdraw its forces from two strategic corridors in Gaza, the Philadelphi corridor alongside Gaza’s border with Egypt and the Netzarim east-west corridor across the territory. Israel offers to downsize its forces in the Philadelphi corridor, with “promises” to withdraw from the area, he said.