Israeli negotiators attending ceasefire and hostage release talks in Doha have expressed “cautious optimism,” even as some gaps between both sides persist, a source familiar with the matter told CNN.

Israeli Prime Minister Benjamin Netanyahu is sending the director of the Mossad foreign intelligence agency to ceasefire negotiations in Qatar, his office said Saturday, in a sign of progress in talks on the war in Gaza.

Mossad director's presence means high-level Israeli officials who would need to sign off on any agreement are now involved. Along with Mossad chief, head of Israel's Shin Bet internal security agency and military and political advisers will also be sent to Qatar to be part of negotiation talks.