Palestinian President Mahmoud Abbas announced Saturday that he would call new presidential and parliament elections at the earliest possible date, in a dramatic and risky challenge to ruling Hamas militants.

The Hamas government, which has drawn crushing international sanctions over its militantly anti-Israel stand, accused Abbas' of carrying out a "coup" against the Palestinian people, who voted the Islamic group into power just 11 months ago. Hamas leaders, including Foreign Minister Mahmoud Zahar, called on Abbas to resign.

Abbas' dramatic announcement — made after he despaired of persuading Hamas to form a more moderate coalition government with his own Fatah Party — further hardened the lines between the two political rivals, at a time when factional fighting threatens to escalate into civil war.

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By putting the Palestinian political situation into limbo for the next few months, it will also paralyze any attempts to build on recent moves to revive peacemaking with Israel.

Abbas, elected separately in 2005, is taking a big political gamble by trying to end his power struggle with Hamas through new balloting. His call for early elections could intensify factional violence. The balloting could also be deprived of legitimacy if Hamas decides to boycott it.

Also, if Abbas does not run again — he has said he'd not seek another term — the moderate camp in Palestinian politics would not have a strong candidate, and could easily lose the presidential vote. His Fatah Party remains in disarray, and might lose to Hamas again in parliament elections.

Aides said the vote would be held as early as March, and that a date would be set within a week.

Abbas' announcement, in a speech at his West Bank headquarters, was met by loud applause from hundreds of supporters.

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"I ... decided to call for early presidential and parliament elections," Abbas said, after outlining months of failed coalition talks with Hamas. "Let us return to the people, to hear their word, and let them be the judge."

"I will look into and have discussed with the Central Election Committee to find the earliest possible way to start preparing for this matter," he said.

Hamas, which swept Fatah from power in January parliamentary balloting, vehemently opposes new elections.

"We are not going to allow elections to take place," said Zahar, the foreign minister from Hamas. "This is a real coup. He (Abbas) has never accepted this government. He has never sat in one government meeting. He has never invited one government minister to meet with foreign ministers.

A Hamas legislator, Mushir al-Masri, said Hamas considers early elections illegal, and independent experts agree that disbanding the government would put Abbas on shaky legal ground.

But Ahmed Yousef, a top adviser to Prime Minister Ismail Haniyeh of Hamas, said the ruling group would protest the election call with peaceful means.

Abbas' speech dashed any hope for a coalition government, he added.

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"Such a government needs a miracle after what President Abbas said today," Yousef said.

Abbas has said repeatedly that his goal is to form a government recognized by the West and to restore badly needed foreign funding, not to topple Hamas. However, Hamas rejects the international community's conditions for resuming aid, including recognizing Israel and renouncing violence.

But imposing a new election on the Islamic militants risks further inflaming already raging tensions between the bitter political enemies. Months of talks on a Hamas-Fatah coalition had held factional violence in check, but after they broke down earlier this month, tensions flared, culminating with a shooting attack on Haniyeh on Thursday.

Abbas aide Saeb Erekat said the president took a brave step.

"I think today Abu Mazen made history," he said, using Abbas' nickname. "I think he saved his people from the prospect of civil war .. We have a crisis. We have an authority with two heads. So what do we do? Bullets or ballots? Abu Mazen said ballots."

Another Abbas aide, Yasser Abed Rabbo, said the president would set the date within a week, and that new elections would be held within three months. However, Erekat said he did not expect elections to be held before June.

The next scheduled vote for parliament is in 2009. Fatah remains in disarray, and polls indicated it is running neck-and-neck with Hamas.

Israeli government spokeswoman Miri Eisin said Israeli Prime Minister Ehud Olmert "respects Abu Mazen and hopes that he will have the capability to assert his leadership over the Palestinian people, and to bring about a government that will comply with the international community's principles."

In the West Bank city of Nablus, hundreds of supporters of Abbas' Fatah movement rushed into the street in celebration, with dozens of gunmen firing in the air. "Abu Mazen, go, go, we are with you until liberation," the crowd chanted.

In Gaza City, dozens of Fatah loyalists and members of his Presidential Guard gathered outside his residence, firing weapons in the air in celebration and chanting: "We are ready to redeem you with our souls and blood, Abu Mazen."

At a Gaza City cultural center, about 500 Fatah leaders watched the speech live on big screen. When the announcement came, they chanted "God is great." Gaza's streets were deserted during the speech.

Hamas has called a demonstration after sunset prayers in Gaza City to condemn the call for early elections. Both Fatah and Hamas are expected to hold simultaneous evening demonstrations in the southern Gaza Strip town of Khan Younis.

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