The four-day cease-fire in Gaza and hostage swap will not begin at least until Friday, Israel and a Palestinian official said Thursday morning.

Israeli National Security Adviser Tzachi Hanegbi indicated the release of at least 50 Israeli and foreign hostages held by Hamas was still on track, but would not happen on Thursday as expected.

"The contacts on the release of our hostages are advancing and continuing constantly," he said in a statement.

"The start of the release will take place according to the original agreement between the sides, and not before Friday."

A second Israeli official said that a temporary halt in fighting would also not begin Thursday.

In the meanwhile, a Palestinian official told the Agence France-Presse (AFP) Thursday that the delay in implementation of a truce in the Gaza Strip between Israeli forces and Hamas was due to "last minute" details over which hostages would be released and how.

The truce had been put back over "the names of the Israeli hostages and the modalities of their release," said the official, who has knowledge of the negotiation process.

The delay is a hammer blow to 2 million-plus Gazans praying for an end to 47 days of Israeli aggression and deprivation, as well as to the families of hostages.

The complex and carefully choreographed deal saw Israel and Hamas agree a four-day truce, during which at least 50 hostages, taken in the Palestinian resistance group Hamas's Oct. 7 incursion, would be released.

For every 10 additional hostages released, there would be an extra day's "pause" in fighting, an Israeli government document said.

Three Americans, including 3-year-old Abigail Mor Idan, were among those earmarked for release.

In turn, Israel would release at least 150 Palestinian women and children and allow more humanitarian aid into the besieged coastal territory after weeks of indiscriminate bombardment.

The deal came after weeks of talks involving Israel, Palestinian resistance groups, Qatar, Egypt and the United States.

Qatari foreign ministry spokesman Majed Al-Ansari said Thursday that implementation of the accord "continues and is going positively."

"The truce agreement that was reached will be concluded in the coming hours," he said.