GAZA CITY, Gaza Strip - Israel delivered its counterdemands yesterday for a deal with Hamas to exchange about 1,000 Palestinian prisoners for a single Israeli soldier held captive by Gaza militants for more than three years.

As families on both sides agonized over the outcome, last-minute differences over who should be freed or sent into exile threatened to imperil the deal.

Israel insists on expelling some West Bank-born prisoners to the Hamas-ruled Gaza Strip or abroad and balks at releasing some inmates high on the Hamas wish list, said a senior Hamas official who spoke on condition of anonymity.

Israeli Defense Minister Ehud Barak appeared to be trying to temper expectations when he told a group of students that returning Sgt. Gilad Schalit was a "top priority" - but "not at any price," a reference to Palestinian prisoners convicted of bloody attacks.

Israel's Channel 10 TV broadcast its coverage of the negotiations over a headline that read, "Not Yet." Israeli media said the deal could take days or weeks to complete.

The Hamas official said that while progress has been made, a deal was not imminent. A Hamas Web site, al-Risalah, said a German mediator was to meet later yesterday with Hamas leaders in Gaza who will "take a final and conclusive decision on what the German mediator brings from his visit to the occupied territories."

Yet another Hamas official said that meeting would take place today.

In recent days, marathon discussions about the swap at the top level of Israel's government conveyed a sense of urgency. However, more than three years of negotiations following the capture of the Israeli soldier have been shrouded in a fog of disinformation and spin, leading to repeated false alarms that a deal is close.

The decision on whether to accept what would be the biggest swap in years is crucial for Hamas, which wrested Gaza from Western-backed Palestinian Authority President Mahmoud Abbas in 2007.

A swap may be the militant group's only means of easing the Israeli-Egyptian blockade that has plunged most of Gaza's 1.5 million residents deeper into poverty and kept them from rebuilding from an Israeli military offensive a year ago. Israel has said it would not consider lifting the embargo until Schalit is freed.

A high-profile prisoner release could also boost the militant group's popularity at the expense of Abbas, who favors a peaceful solution to the conflict with Israel but has little to show for years of negotiations.

On the flip side, Hamas has proved resistant to compromise in the past, and may refuse to give up the soldier, its only bargaining chip, if offered less than it demands.

Israel wants to deport dozens of prisoners, according to a Palestinian official who said he has been briefed on the negotiations. Another Palestinian, who is close to the talks, said the German mediator arranged with six countries to take the freed prisoners.

Both spoke on condition of anonymity because of the sensitive nature of the talks.

Hamas has tried to lower the number of prisoners to be exiled but has shown flexibility on the issue, saying it would let individual prisoners decide whether to accept deportation.

Two officials, one in Gaza and one in the West Bank, said that Israel refuses to release several prisoners high on Hamas' wish list. There were conflicting reports about what the proposed deal would mean for Marwan Barghouti, a hugely popular Palestinian uprising leader seen by many as a potential successor to Abbas.

One official said that Israel wants to exile him. Another said it refused to release him at all. Barghouti is serving multiple life sentences for involvement in fatal attacks against Israelis.