GAZA CITY — Khaled Meshal, the political leader of Hamas, gave a defiant speech on Saturday, vowing to build an Islamic Palestinian state on all the land of Israel, the West Bank and the Gaza Strip.

Speaking before tens of thousands of supporters to celebrate the 25th anniversary of the founding of Hamas, Mr. Meshal said the Jewish state would be wiped away through “resistance,” or military action. “The state will come from resistance, not negotiation,” he said. “Liberation first, then statehood.”

His voice rising to a shout, Mr. Meshal said: “Palestine is ours from the river to the sea and from the south to the north. There will be no concession on any inch of the land.” He vowed that all Palestinian refugees and their descendants would one day return to their original homes in what is now Israel.

“We will never recognize the legitimacy of the Israeli occupation, and therefore there is no legitimacy for Israel, no matter how long it will take,” he said. “We will free Jerusalem inch by inch, stone by stone. Israel has no right to be in Jerusalem.” He also promised Palestinian prisoners held in Israel that they would be freed using the same methods that had worked in the past — the kidnapping of Israelis and Israeli soldiers, like Gilad Shalit, who was released last year in a prisoner exchange after five years as a hostage.