GAZA CITY , Gaza ( CNN ) -- A truce between Israel and Gaza 's Hamas leaders will take effect Thursday and last for six months , Hamas officials said Tuesday . Palestinian Hamas security men stand to attention at a training academy in Gaza City last week . Israeli officials , however , stopped short of confirming that a cease-fire agreement has been reached . `` It 's still early to announce an agreement of calm , '' Israeli Defense Minister Ehud Barak said in a statement . `` When it starts , if it starts , it 's hard to say how long it will last . The test will be how it 's implemented . '' Hamas senior official Mahmoud Zahar and Hamas negotiator Khalil al-Hayya announced the Egyptian-brokered agreement at a news conference in Gaza . They said it will begin at 6 a.m. Thursday ( 11 p.m. Wednesday ET ) . On Sunday , Israel gradually will start to open its border crossing terminals , the Hamas officials said . Asked about initial reports of a cease-fire , one Israeli official would not confirm whether an agreement had been finalized but said any truce would involve a sequential process . Watch what truce may mean in Gaza » . The official said Israel would reopen some of its terminals along the Gaza border after calm had been established . He said Israel is still calling for the release of Cpl . Gilad Shalit as part of a broader cease-fire . Gaza militants kidnapped Shalit in June 2006 . Egypt has been trying to broker a truce between Hamas and Israel for months . Militants in Hamas-controlled Gaza have pummeled Israel with thousands of rocket and mortar attacks , prompting Israeli military operations in the Palestinian territory . Referring to the Egyptian mediation efforts , Barak said , `` It 's important to exhaust the possibility . `` The IDF [ Israel Defense Forces ] is prepared for any developments , but it is important to attempt to achieve a period of calm to bring back the peace and quiet for the [ Israeli ] people who live around Gaza in Sderot and Ashkelon and to try and renew negotiations for the release of Gilad Shalit . '' Militants in Gaza have launched more than 2,300 mortars and rockets since the start of 2008 , more than the 2,000 launched in all of last year , according to Israeli military figures . While most of the attacks do not result in casualties , three Israelis have been killed in rocket and mortar strikes in recent weeks . The Israeli military responds to the attacks by carrying out airstrikes and ground operations in Gaza that target militants , but many times lead to civilian casualties -- further inflaming the Palestinian leadership . Israel also has restricted supplies of gasoline , diesel and electricity to Gaza , limited the amount of food and other goods entering the strip and made it virtually impossible for manufacturers and farmers in Gaza to export anything to the outside world . Hamas seized control of Gaza last year after routing Palestinian security agencies under the control of Palestinian President Mahmoud Abbas and his Fatah movement . The ouster forced Abbas to dissolve the Fatah-Hamas unity government , but Fatah still controls the West Bank . Representatives from the rival factions met recently in Senegal for talks aimed at restoring the political and territorial split . Earlier this month , Abbas called for `` national unity '' talks with Hamas with the goal of producing new elections for the Palestinians , who elected a Hamas-led Palestinian Authority government in a U.S.-backed vote in 2006 . Meanwhile , Abbas ' Western-backed government is working toward a peace agreement with Israel . The Bush administration has said it wants the two sides to reach an agreement by the end of the year . CNN 's Shira Medding contributed to this report .
NEW : Hard to say how long any cease-fire will last , Israeli defense minister says . Israel has not confirmed cease-fire pact . Comment: Hamas took control of Gaza a year ago .