— Hamas officials, in their first public rally since a truce with Israel, vowed Thursday to never give up arms and to reignite war if Israel does not accept their demands to lift an economic blockade of the Gaza Strip.

The defiant rhetoric, delivered as supporters chanted, “Blow up, blow up Tel Aviv,” came on the final day of a three-day truce that has brought a rare calm to the region after a month of violent conflict. Hamas and other Palestinian factions are now indirectly negotiating with Israel for a lasting cease-fire.

But little headway has been made, according to diplomats and local news media reports, and mediators were seeking Thursday to extend the cease-fire in an attempt to reach a breakthrough, particularly on Hamas’s core demands that Israel lift the blockade and that border crossings to Israel and Egypt be opened.

Thursday’s rally appeared to be planned by Hamas to put more pressure on Israel and its allies to accept the militant group’s demands. With a turnout of a few thousand people, the demonstration was much smaller than the massive crowds Hamas has attracted in the past since it seized power in Gaza in 2007. But it was unclear whether the numbers reflected waning support or, rather, the sense of fatigue and uncertainty that has gripped Gazans who are grappling with enormous devastation and loss.

“The war is not over yet,” Mushir al-Masri, a top Hamas official, told those gathered. “Our fighters are still in the field, in their frontline positions. Our tunnels still exist, and they reach into Israeli territory. If Israel doesn’t agree to our demands, we will come there.”

1 of 75 Full Screen Autoplay Close Aug. 8, 2014 Aug. 7, 2014 Aug. 6, 2014 Aug. 5, 2014 Aug. 4, 2014 Monday August 3, 2014 Sunday Skip Ad × As cease-fire continues, Palestinians inspect damage and Israeli troops return home View Photos The 72-hour cease-fire, which took effect at 8 a.m. Tuesday, was agreed to late Monday by both Israel and Hamas following talks in Cairo. Caption Talks to extend the three-day truce between Israel and Hamas were making little headway in Cairo. Aug. 9, 2014 Smoke rises in Gaza City after an Israeli airstrike. The hostilities between Hamas and Israel entered their second month with more than 1,900 dead. Dusan Vranic/AP Buy Photo Wait 1 second to continue.

As he spoke, the crowd cheered. Some clutched Hamas’s green flag, while others held a white one emblazoned with an AK-47 — the standard of theIzzedine al-Qassam Brigades, Hamas’s military wing. Some parents had dressed their children as fighters — in camouflage fatigues and green bandanas with plastic toy guns.

The rally and rhetoric underscored the significant divide between what Israel and Hamas expect from each other in the negotiations being held in Cairo. Israel wants Gaza demilitarized before discussing Hamas’s demands, which also include a release of Palestinian prisoners in Israeli jails and greater fishing rights in the Mediterranean.

But Masri on Thursday declared that Hamas had defeated Israeli troops during the war and that the group would never give up arms. Instead, he and other Hamas officials warned Israel and its allies not to “blackmail” the Palestinian delegation into compromising their demands.

“What the occupation has failed to achieve on the battlefield, they are trying to achieve on the negotiating table,” Masri said. “They will never force us to abandon our weapons, both on the battlefield and in negotiations.”

In a conference call with journalists, Israeli Brig. Gen. Mickey Edelstein, who commands the army’s Gaza Division, said Israel was prepared if Hamas chose to wage war again.

“We are ready for any scenario,” he said. “If Hamas will want to keep on fighting, we are ready for this.”

More than 1,900 Palestinians were killed between the July 8 outbreak of war and the present truce, more than 75 percent of them civilians, according to the United Nations. Sixty-four Israeli soldiers were killed, along with three civilians caught in the explosions of militant rockets or mortars fired from Gaza into Israel.

Orly Halpern in Jerusalem contributed to this report.