GAZA CITY: The Islamic militant group Hamas is marking the anniversary of its 1987 founding with celebrations Monday, hoping to show it still has broad support despite four years of rule that have led Gaza into war, poverty and isolation.

Gaza was decked out in Islamic green, with Hamas flags fluttering from roofs and lampposts. Hamas' radio and TV stations exhorted Gazans to attend a mass rally after Muslim midday prayers.

Since last year's anniversary, which drew tens of thousands of supporters, Hamas has suffered several setbacks, key among them Israel's military offensive on Gaza last winter.

The three-week war, launched to halt rocket fire from Gaza, failed to dislodge Hamas but made it harder for the militants to govern.

Hamas has been unable to rebuild homes, sewage lines and water pipes destroyed in the assault because Israel and Egypt continue to enforce a border blockade. Basic goods like food and some medicines are allowed into Gaza, but construction materials are not.

The closure was first imposed in June 2006, after Hamas-allied militants captured an Israeli soldier, Gilad Schalit. It was tightened a year later, when Hamas overran Gaza, ousting forces loyal to Western-backed Palestinian President Mahmoud Abbas.

As it marks its anniversary, Hamas faces an impasse on two interconnected deals that could pry Gaza's borders open — a swap trading Schalit for hundreds of Palestinian prisoners held by Israel, and a power-sharing deal with Abbas and his Fatah movement. A German mediator appears to have achieved some recent progress on a prisoner swap with Israel, but there has been no apparent headway in the Palestinian unity talks.

Ghazi Hamad, one of the more pragmatic Hamas officials, said Hamas would not be able to rule alone indefinitely. "No one can cancel Hamas, no one can expel Hamas from the political game ... but Hamas cannot play alone and Fatah cannot play alone," he said.