(Reuters) - Israel announced a unilateral ceasefire in its offensive against Hamas in the Gaza Strip on Saturday.

Following are some implications of Israel’s decision: * While Israel said in announcing its decision that all goals in its Gaza offensive had been met, the threat of rockets being fired after the ceasefire starts remains high.

* Hamas has said the ceasefire is effectively meaningless and it will continue “resistance” until Israel pulls its troops out of the Gaza Strip and opens border crossings to allow in food, aid and other materials. Israel has given no timetable for withdrawal or border openings.

* Other militant groups in Gaza have also said the ceasefire is meaningless and they will continue “resistance” against Israel, which is likely to include rocket fire. Thus, Israel’s main stated goal may be challenged, at least in the near term.

* Israel has said that if Hamas and other groups do continue rocket attacks, it will resume operations. Given the likelihood of rockets continuing, Israel’s mettle is certain to be immediately tested.

* The fact Barack Obama is to be sworn in as the new U.S. president on Tuesday is widely perceived to have had an impact on Israel’s decision-making. Israel is keen to ensure it remains on sound terms with its closest ally. That may make it keen to hold its fire even if Hamas does not.

* International pressure -- from the U.N. and European states -- will also be heavy on Israel hold fire and set a timetable for pulling its troops out of Gaza. Failure to do either of those things could play into Hamas’s hands.

* Yet Israel is calculating that by taking unilateral action, it puts pressure on Hamas to follow suit. If Hamas continues rocket fire, the Islamists may be perceived as the aggressors and Israel may feel justified in resuming operations.

* The three-week offensive resulted in more than 1,200 Palestinian dead, including 410 children. Thirteen Israelis were also killed. Despite the toll, Israel is hoping its decision on a ceasefire will offset some of the worldwide criticism it has faced for the onslaught, including suggestions by U.N. officials that its actions should be investigated for war crimes.

* Part of Israel’s decision-making is also linked to parliamentary elections on February 10.

* Both the defense minister, Ehud Barak, and the foreign minister, Tzipi Livni, are candidates in the election. They are hoping a ceasefire, with Israel having met all its goals, will stand them in good stead with the electorate. They will be anxious, therefore, to show they have succeeded in substantially ending the rocket fire that has disrupted life in the south.

* Their rival, conservative former Prime Minister Benjamin Netanyahu, is already ahead in polls and tipped to win the election. Any perceived failures in Gaza could strengthen his electoral chances as a hawk who opposed Israel’s move to withdraw its forces from the Gaza Strip in 2005.