Hamas said Thursday it was ready to negotiate the the next phase of the ceasefire in the Gaza Strip, after a swap in which it handed over what it said were the remains of four hostages in exchange for the release of more than 600 Palestinian prisoners held by Israel.

Hamas has rejected a proposal by U.S. Middle East Envoy Steve Witkoff to extend a first phase of the ceasefire and release more Israeli hostages. Israel's Prime Minister Benjamin Netanyahu said on Sunday there would be no possibility of continuing the ceasefire without Hamas releasing hostages.

The first phase of the ceasefire that paused 15 months of brutal warfare between Israel and Hamas is set to end on Saturday.

With the return of the four bodies, Israel has now received all 33 hostages to be handed over in the first phase of the ceasefire deal.

Israel delayed the release of hundreds of Palestinian prisoners without explanation Saturday after Hamas released the last six living hostages expected under the ceasefire 's first phase, with a week remaining in the initial stage.

Israeli Prime Minister Benjamin Netanyahu has vowed revenge for what he described as a “cruel and malicious violation” of the ceasefire agreement after a body that Hamas released as part

Israel wants to extend the first phase of the deal with Hamas, rather than begin negotiations over the more politically fraught second stage.

Officials from Israel, Qatar, Egypt and the United States have been involved in negotiations on the second phase in Cairo.