Hamas leader Ismail Haniya says the Islamist movement is committed to Palestinian national reconciliation in order to fight the Israeli occupation.
He was addressing tens of thousands of supporters at a rally in Gaza City to mark the group's 23rd anniversary.
Palestinians are divided between Hamas, which runs the Gaza Strip, and Fatah which controls the West Bank.
The rift dates back to 2007 when they fought each other in Gaza's streets. Mediation efforts have so far failed.
"Today, on the anniversary of its establishment, Hamas stresses that it is committed to the principle of reconciliation," Mr Haniya told throngs of supporters who filled the streets of Gaza City, waving green banners.
"Reconciliation is a must so that the Palestinian people recover their unity in confronting the occupation," he said.
Israel occupied the West Bank and the Gaza Strip during the 1967 Middle East war. It withdrew its troops and settlers from Gaza in 2005, but heightened its blockade on the territory after Hamas came to power in 2007.
Hamas is designated a terrorist organisation by Israel, the US and the EU, but it is seen by its supporters as a legitimate resistance movement.
At the rally, Mr Haniya repeated his group's pledge never to recognise Israel, saying the Palestine Liberation Organisation (PLO) headed by President Mahmoud Abbas had made a "historic mistake" by doing so.
In September, the group vowed to step up attacks against Israel after Mr Abbas entered a fresh round of negotiations with Israeli Prime Minister Benjamin Netanyahu, which kicked off in Washington in the presence of President Barack Obama.
Those talks have since faltered over Israel's refusal to stop the building of Jewish settlements in occupied Palestinian territories. The settlements are illegal under international law, but Israel disputes this.
Mr Haniya had raised speculation last month about a change in the Hamas charter - which calls for Israel's destruction - by suggesting the group could accept a referendum on a peace treaty that gives the Palestinians a state based on the 1967 ceasefire lines.
But at the rally, he said such a truce would entail "no recognition of Israel and no concessions over any part of the land of Palestine".
The Islamist group has controlled Gaza since routing the rival Fatah faction of Palestinian leader Mahmoud Abbas from there in June 2007.
Hamas, an Arabic acronym for the Islamic Resistance Movement, was created in 1987 after the beginning of the first intifada, or Palestinian uprising, against Israel's occupation of the West Bank and Gaza.
It is still holding Israeli soldier Gilad Shalit, captured by militants during a cross-border raid in June 2006.