Israel's assault on Gaza's Hamas rulers has destroyed at least $1.4 billion worth of buildings, roads, pipes, power lines and other infrastructure in already impoverished territory, Palestinian surveyors estimate. Arab and Western countries will be called on to foot much of the bill to rebuild - which Palestinian economists say could take five years or more. The IDF says it has bombed over 2,500 Hamas-linked targets since December 27, including 250 tunnels the terror group used to smuggle in arms as well as large amounts of weapon stockpiles and rocket launcher squads. Even with the Israeli offensive going full throttle, the international community is starting to tackle the formidable postwar challenge. Europe's top four fundraisers for the Palestinians - the foreign ministers of France and Norway, the European Union external relations commissioner and the international Mideast envoy - are meeting in Paris on Thursday to discuss Gaza's reconstruction and the possibility of holding a new donors' conference. The last one, held in December 2007 at a time of renewed Mideast peace hopes, secured promises of $7.7 billion in aid through 2010. However, donors may have a tougher time contributing large sums in the current global financial crisis. Another concern is whether a cease-fire deal will lift the blockade Israel and Egypt imposed on Gaza after Hamas seized the coastal strip in June 2007 and ousted the forces of Palestinian Authority President Mahmoud Abbas. "You cannot rebuild Gaza without open borders," said Tor Wennesland, the top Norwegian diplomat in the Palestinian territories. Yet ending Gaza's lockdown will require compromises that seemed impossible before the Israeli offensive. Hamas will have to relinquish some control by allowing a buffer force to deploy on the crossings, most likely international monitors, Abbas' troops or both. Gatekeepers Egypt and Israel say there's no way they'll agree to give Hamas, a violent Iranian proxy, a final say over who and what enters and leaves Gaza. But if they accept a new border regime with monitors, that would inevitably strengthen the Islamist group's rule over Gaza. In any arrangement, rivals Abbas and Hamas will have to find a way to work jointly, not just to run the crossings but to oversee reconstruction projects. The two have been unable to come up with a power-sharing formula since Hamas defeated Abbas's Fatah movement in the 2006 parliament elections.