For the first time in a decade, the founders and top political leaders of Hamas gathered on the same stage Saturday, vowing to go on fighting Israel and claiming victory for its impending withdrawal from the Gaza Strip (search).

In a direct challenge to the Palestinian Authority, the militant groups' top brass said it rejects the idea of a sole decision-making body for the area and insists it has the right to possess weapons.

Tensions between the Palestinian Authority and Hamas have heated up in the days before Israel begins its withdrawal from the Gaza Strip and four West Bank settlements, with each trying to claim victory for the pullout.

On Saturday, Hamas leaders positioned themselves in front of the group's logo and a green Islamic flag to send a message that they have the right to possess weapons and to claim responsibility for pushing Israel out of the Gaza Strip.

The Hamas news conference comes just a day after the Palestinian Authority (search) held its first official celebration — with the attendance of Palestinian leader Mahmoud Abbas — of Israel's withdrawal from the Gaza Strip and four West Bank settlements.

Speakers at Friday's ceremony made it clear that all celebrations of the withdrawal would take place under the official Palestinian banner — the red, black, green and white flag — a message to Hamas.

Tens of thousands of Palestinians on Friday crowded Gaza City's small harbor to celebrate the withdrawal, waving flags and hearing promises from their leader that the West Bank and Jerusalem will be next.

Abbas, surrounded by security guards, told the crowd: "From here, from this place, our nation and our masses are walking toward the establishment of an independent Palestinian state with Jerusalem as its capital."

Yet tensions between Abbas and the militant group Hamas became apparent when Cabinet minister Mohammed Dahlan said the Palestinian flag must be the official banner at all celebrations. He did not refer to Hamas directly, but the group has said it plans its own military-style celebrations, and is sewing thousands of its own green banners.

"This era is the era of unity, and the era that will end any competition or disagreement," Dahlan told the crowd.

Hamas, on Friday, invited TV cameramen for the first time to film about 1,000 militants training ahead of the pullout. The release of the pictures of militants rappelling from high-rise walls and jumping through hoops of fire was seen as a challenge to the Palestinian Authority.

But it was unclear whether the training — which included the infiltration and attack of a Jewish settlement — meant the group would fire on withdrawing Israeli troops and settlers, despite demands by the Palestinian leadership that they allow Israel to evacuate the area quietly.

Israel is to begin its withdrawal from Jewish settlements in Gaza early Monday and later pull out of four West Bank settlements. The Israeli Defense Ministry (search) said Friday it wants to complete the withdrawal by Sept. 4.

Israeli Prime Minister Ariel Sharon suggested in an interview published Friday that Israel could eventually relinquish more West Bank settlements. He reiterated, however, that Israel would keep major West Bank settlement blocs. "Not everything will be there. The issue will be raised during the final status talks with the Palestinians," Sharon told the Yediot Ahronot newspaper.

Sharon said he is convinced the withdrawal from Gaza will benefit Israel in the long run. "I have no regrets," he told Yediot. "Even if I had known the level of (settler) resistance, I would have done it."

When Sharon decided more than a year ago to withdraw from Gaza, captured 38 years ago, he reasoned that would make it easier for Israel to hold on to the major West Bank settlement blocs, where most of the 240,000 settlers live. In all, 9,000 settlers are to be uprooted.