Israel should resume military operations against Hamas in the Gaza Strip when the cease-fire expires in three weeks to increase pressure on the terrorist group that could lead to a renewal of talks for St.-Sgt. Gilad Schalit, several high-ranking defense officials said Wednesday. On December 19, the cease-fire that went into effect at 6 a.m. on June 19 will officially end. Israeli assessments vary regarding whether Hamas will want to extend the truce or allow it to collapse and return to full-scale terror operations against Israel. One school of thought is that Hamas will prefer to extend the cease-fire to solidify its control over Gaza and secure the full reopening of the crossings, including the Rafah Border Terminal with Egypt. Others raise the possibility that Hamas will decide to renew its own rocket attacks on Israel. The most recent attacks are attributed to smaller groups. "It is difficult to tell what they will do," one senior defense official told The Jerusalem Post Wednesday. "What is certain is that December 19 is turning into a very important date." The term of Palestinian Authority President Mahmoud Abbas also comes to an end soon, on January 9, and in Israel there is concern that Hamas may renew the violence then in protest of Abbas's expected refusal to vacate his post for a Hamas official. Defense Minister Ehud Barak has ordered his top aide Amos Gilad to hold talks with Egypt in an effort to extend the cease-fire. On Wednesday, Deputy Defense Minister Matan Vilna'i said Hamas appeared to be making efforts to rein in the various factions that have been behind the latest spate of rocket attacks. Top IDF officers have suggested, however, that Israel should consider renewing operations in Gaza since "military pressure is one of the effective forms of leverage Israel has to get Hamas to renew negotiations for the release of Schalit." Since the truce went into effect in June, Egyptian-mediated talks have mostly been frozen despite Barak's claim - before Israel agreed to the truce - that it would create an opportunity to advance the soldier's release. "We need leverage over Hamas," one top officer said. "And there is no better leverage than military pressure." Also on Wednesday, Barak decided to allow some 60 trucks carrying humanitarian supplies to pass into the Gaza Strip, even though the crossings were still officially closed due to repeated Kassam rocket attacks. Barak's decision came following international pressure on the security establishment to allow the aid through. Palestinian fuel official Mahmoud Khazundar said that shipments of cooking gas were also renewed on Wednesday morning and that 70 tons were expected to enter the Strip. Meanwhile, the United Nations and other aid agencies appealed to the international community to send $462 million in emergency assistance in 2009 to address what they said was a humanitarian crisis in the Palestinian territories. Most of the money will be used for food and cash handouts, said Maxwell Gaylard, local head of the UN Office for Coordination of Humanitarian Affairs. A total of 159 emergency programs are planned in areas such as health, education, food, water and sanitation. It is the seventh annual request for emergency funds, in addition to hundreds of millions of dollars in normal operating budgets. "Little, if anything, has been achieved," said Filippo Grandi, deputy commissioner of the UN Reliefs and Works Agency, the main UN body caring for Palestinian refugees. "Little, if anything, has been felt by the people with whom we work." Grandi lamented the need to spend funds on emergency responses instead of long-term development projects. He said the situation was especially dire in the Gaza Strip, which was stifled by Israeli and Egyptian border closures and where half the population lived in severe poverty. Last year, the UN asked for a similar amount of emergency aid. Officials said they raised nearly 70 percent of the funds they sought. Kuwait, the European Union and the United States were last year's largest donors, staff said. Grandi said he feared the global economic crisis would lead to cuts of as much as a third in operating funds for UN agencies in the Palestinian areas next year. He said the Israeli closure had prevented UN agencies from delivering even the minimal amount of aid needed to meet basic needs in Gaza. AP contributed to this report.