And unilaterally, as the BBC reports.  Rather than get entangled in a cease-fire agreement that Hamas will likely violate as soon as they possibly can, the IDF will simply stop in place at an undetermined H-Hour.  If Hamas stops attacking, Israel will continue, but if not, the IDF will be in place to continue its operations:

Israeli sources told the BBC’s Middle East editor, Jeremy Bowen, that Mr Olmert would announce an end to offensive military operations from “H-Hour”, the exact timing of which is not yet clear.

In a televised address set for 2200 (2000 GMT), Mr Olmert was expected to link the move to Israel having achieved its goal of curtailing rocket fire from Hamas-linked militants, the sources said.

If rocket fire continued after “H-Hour”, Israel would respond, the sources said.

If there was a single incident, Israel would hit back “surgically”; if there were more attacks Israel would go back on the offensive, they said.

The sources stressed that this was a unilateral action by Israel.

Israeli sources tell the BBC that Olmert and his Cabinet decided to rely on assurances from Europe and the US that they could partner with Egypt to stop the smuggling of rockets and mortars into Gaza.  That may have played into the decision, but at some point, the IDF may have recognized the law of diminishing returns.  If they have successfully reduced the Hamas positions they know and have fully exploited their intelligence, the need to continue their offensive ends.

In this instance, a cease fire might benefit the Israelis more than Hamas anyway.  It allows for intelligence sources to develop on enemy positions, as it’s difficult for people to transmit that while the guns fire into their neighborhoods.  It also puts pressure on Hamas to knuckle under to Israeli demands, and an failure to honor the cease-fire gives Israel better standing to continue its offensive.

Hamas, for its part, has not stopped.  They fired seven more rockets into Israel, showing that they still have offensive capabilities.  However, Hamas has split on the issue of a cease-fire, with its international leadership rejected the notion and the Gazans hoping for some sort of respite.  The unilateral Israeli cessation may put enough pressure on this division to cause a significant fracture, both within Hamas and between Hamas and their Iranian sponsors.

In any case, the Israelis continue to control the situation, and Hamas is left with few options, and no good ones.