Q&A-Why might Israel end Gaza attack without a deal?

JERUSALEM (Reuters) - Israeli leaders may decide on Saturday evening to declare a halt to their three-week-old offensive on Hamas-led Islamist militants in the Gaza Strip.

An end to the attack may be announced without any truce deal with Hamas, which has proposed a one-year ceasefire provided Israel meets certain conditions.

Here are some questions and answers about such a move.

Q - Why would Israel pull out unilaterally?

A - Talk of a "unilateral" decision may be a negotiating ploy. For its own political prestige, Hamas wants to be seen making a deal. Threatening to deprive them of that by ignoring their proposals could prompt Hamas to chase a deal by agreeing to Israel's key demands, for example, an open-ended ceasefire.

Q - Won't Israelis question a unilateral ceasefire?

A - It could have positive public relations value. Many Israeli voters -- they go to the polls in three weeks -- find the idea of negotiating with Hamas distasteful even at arm's length, because Hamas is committed to destroying Israel.

Q - Is there something more behind it.

A - It may simply be the first part of a phased package of measures to end the war. Provided Hamas militants held their fire as well, it would address mounting international demands to ease the suffering of civilians in Gaza. The de facto truce could then be bolstered by agreements to secure the Gaza-Egypt border to meet Israeli demands that smuggling of arms via border tunnels is stopped. Then there could be a further agreement to open border crossings controlled by Israel, which has maintained a blockade of Gaza since Hamas took over there in 2007

Q - If that's the case, why not do such a deal now?

A - Some Israeli officials are outright hostile to peace talks mediated by Egypt. They say this undermines key war aims: to weaken, isolate and intimidate Hamas. They want to deprive Hamas of the political gains it would get from a negotiated truce accord, that would also likely require the Jewish state to throw Gaza's border crossings open, as Hamas demands.

Q - Are there other potential advantages for Israel?

A - If there's no formal ceasefire with Hamas, Israel and Egypt keep control over Gaza's borders. They could use Gaza's eventual reconstruction to try to re-establish the authority of the Western-backed Palestinian president, Mahmoud Abbas, who is committed to making peace with Israel and establishing a Palestinian state in the West Bank and Gaza. Hamas drove pro-Abbas forces from Gaza in June 2007 and has refused to consider letting them return to control the crossings.

Q - Isn't it better to have Hamas's agreement to a truce?

A - Israel hopes Gaza militants have been taught a lesson and will think twice before starting a new fight. Hamas remains a force, but Israeli intelligence thinks the offensive, in which Israel has killed over 1,150 Palestinians, has weakened Hamas and reduced its rocket arsenal. Israeli bombing also destroyed tunnels that Hamas could have used to rearm quickly.

(Reporting by Adam Entous; Editing by Douglas Hamilton)