JERUSALEM, March 30-- Israel was supposed to release the forth, and final, group of Palestinian prisoners on Saturday, but as of Sunday there were still no signs of an impending release.

The release of 26 prisoners, all held in Israeli prisons since before the start of the Oslo process in 1993, was intended to be the fourth and last release of prisoners that Israel agreed to. It 's a confidence-building measurement when U.S. Secretary of State John Kerry announced the resumption of the Israeli-Palestinian negotiations in June last year.

The timing of the release was planned to coincide with Kerry presenting a framework agreement for a final peace deal. However, despite intense diplomatic efforts by Kerry and other American officials, the Israelis and the Palestinians still disagree on too many issues for Kerry to be able to present such an agreement.

Although the prisoners were not released on Saturday, Palestinian officials said that a release might happen later in the week. Also on Sunday the Israeli newspaper Haaretz reported that Israel could be willing to release an addition 400 prisoners to keep the talks going.

So the decision not to release should, at least for the moment, be seen more as a temporary holdup rather than a breakdown of the negotiations. In addition Kerry, who is heavily invested in the negotiations, might visit the region in the coming days after his current visit to Paris.

Analysts said that although the Israeli decision was based on its frustrations with the lack of Palestinian reciprocation for Israeli gestures, the negotiations are likely to continue because it is in both sides' interests that they do. Neither side wants to be blamed for causing the talks to fail.

Dr. Kobi Michael of the Institute for National Security Studies in Tel Aviv said that not releasing the prisoners was a "very reasonable and logical move because if there isn't any continuation of the negotiations so why to go on with the release of the prisoners."

He was alluding to the concern in Israel that the Palestinians, especially since Kerry's plan has not been finalized, might opt to hold future negotiations and hence Israel would get nothing in return for the prisoners.

However, Dr. Kobi cautioned that "we have to take everything very carefully because there is a lot of noise around the current events, and we really don't know the real details."

"Something else is going on and we have to be patient and should wait a couple of days in order to understand what is going on here," he added.

The professor outlined a scenario where by the end of this week there is an agreement between the parties, including the United States, about the continuation of the negotiations with a gesture from Israel; maybe it will not be prisoners, maybe it will be something else like the freezing of the settlement.

Israel's releasing Palestinian prisoners was one of the three confidence-building gestures after Kerry announced the resumption of the Middle East peace talks last year. The other two were a settlement freeze and a plan for borders with a Palestinian state.

However, as Israel has released three groups of prisoners with nothing in return from the Palestinians, Eran Vigoda-Gadot, a professor of the University of Haifa, said that the degree of flexibility and freedom is narrowing, and that Israel is going towards a very critical stage of the negotiations.

"Things must clear up very soon and the opposition from within his (Netanyahu's) government is becoming stronger with lots of rational arguments about what Israel is getting out (the releasing of prisoners)," he said.

He added that the rightists are arguing along the lines of "are we going anywhere or is it just another intermediate process where we give and no one gives in return."