Palestinian militants in the Gaza Strip may be planning to execute terror attacks against Israel which would require responsive military operations like the one carried out last week, Israeli defense officials said on Sunday.

Over the next two days, Defense Minister Ehud Barak will determine whether to reopen the border crossings with Gaza, which were shut down last Wednesday after Gaza militants resumed rocket fire on the western Negev.

After nearly two days of quiet, militants in Gaza fired a Qassam rocket at the western Negev, but it exploded in Palestinian territory. Some 70 rockets were fired from Gaza between last Wednesday and Saturday, in response to an Israel Defense Forces raid on the coastal territory which killed at least six militants.

Sunday marked the first resumption of calm since the raid and the rocket barrages. Israel and Gaza are still technically in the midst of a six-month old cease-fire, which both sides have breached since its implementation last June.

The critical question facing Israeli defense officials now is what will become of the truce in the coming months.

Hamas has declared that the truce ends on December 19 and is up for negotiation only if Israel keeps its word to expand the calm to the West Bank.

Israel said it never committed to such a deal and said that the truce has no official "expiry date." Egypt, which mediated the temporary truce, apparently sides with Israel on this matter.

Hamas' consideration for maintaining the calm are clear: The group believes the cease-fire serves its own well-being in allowing it to establish a firm basis as the prime political power in the Gaza Strip. Continuing rocket fire only increases the chances that Israel will close off its borders - and while Hamas relies on the smuggling of weapons and trade from Egypt, long-term closures have great effect on the comfort of the territory's residents.

Some Israeli military officials estimate that Hamas would prefer to blur the disagreement over these details and continue the truce, for the same political and security reasons it agreed to the calm in the first place.

Other Israeli officials claim there is high potential for renewed clashes between December 19 and January 9 - the date Palestinian President Mahmoud Abbas' term ends.

The same officials believe that as tensions between Hamas and Abbas' rival Fatah movements resume with the end of the president's term, so too will rocket fire on the western Negev.

Meanwhile, a senior Hamas official said Sunday that the group would not implement a long-term truce with Israel for the time being.

The offer "was not canceled," Mahmoud al-Zahar said, but added that there was "no room to implement it for the time being" since "there is no one to talk about this proposal with on the other [Israeli] side."

He said a long-term truce was "a project that can be developed when there are intentions."

The Hamas long-term truce offer was first made by the organization's late spiritual advisor, Ahmed Yassin, who suggested a 20-year-long ceasefire, without recognizing Israel's right to exist, in return for an Israeli withdrawal from lands captured in the 1967 Six-Day war.

Zahar's remarks were made a day after Hamas leader Ismail Haniyeh said his government could accept a Palestinian state only in the West Bank, the Gaza Strip and East Jerusalem, the territories captured by Israel in the 1967 war.