GAZA CITY, Gaza Strip - Gazans rejoiced in the streets to celebrate a Hamas-Fatah power-sharing deal they hope will avert civil war, but Palestinian officials preached patience Friday, saying implementing the agreement would be a challenge.

The agreement received a muted response from American and European officials, who said it was too early to decide whether to lift the crippling international sanctions on the Hamas-led government.

The rivalry between Hamas and Fatah began last year when Hamas won parliamentary elections and formed a Cabinet, splitting power with President Mahmoud Abbas of Fatah. The friction between the two groups paralyzed the government and eventually exploded into fighting that killed more than 130 Palestinians.

The two sides have tried unsuccessfully for months to reach a deal amid the violence. The success conclusion of an agreement in Saudi Arabia on Thursday sparked elation among people in Gaza.

"We have left behind all those black days forever and started a new page on a new government and a new way in Palestine," Abbas said.

Celebratory gunfire could be heard in several parts of Gaza City and fireworks lit up the sky. Some drivers flew both green Hamas flags and yellow Fatah banners from their cars.

"For four or five days we've been holding our breath. God willing, this is a permanent agreement, not a temporary truce," said Mahmoud Qassam, 27, a fish vendor in Gaza City. "We hope this will lead to lifting the siege," a reference to the economic sanctions.

The West demanded that Hamas recognize Israel's right to exist, accept past peace agreements with the Jewish state and renounce violence in order to escape the sanctions.

Hamas has refused those demands. The platform of the coalition government agreed to on Thursday says only that the government pledges to "respect" previous deals, instead of "committing to" them, as Abbas initially demanded. It makes no reference to recognizing Israel or renouncing violence, and it remains unclear whether the U.S. and Israel will be ready to deal with the new coalition.

U.S. and Israeli acceptance is crucial to the deal's success. Unless they are convinced Hamas has sufficiently moderated, the West is unlikely to lift the sanctions, and it will be difficult to advance the peace process.

Deputy White House press secretary Dana Perino thanked Saudi King Abdullah for bringing the parties together but said "we have not actually seen the agreement."

"Clearly the violence ... has served no one and, in fact, it's only served to kill many innocent people. And so we hope that the violence that has ebbed, that that will hold off. And then when we get a chance to look at the agreement in more detail, then we'll be able to say more at that point," Perino said.

The Quartet of Middle East negotiators -- including Secretary of State Condoleezza Rice, U.N. Secretary-General Ban Ki-moon, Russian Foreign Minister Sergey Lavrov and top European Union officials -- held a conference call Friday to discuss the agreement, the EU said.

EU spokeswoman Emma Udwin said all parties agreed that there was a need "to take the time to consider, to see what the agreement is and how it is going to be implemented," before deciding on lifting the embargo.

Israeli government spokeswoman Miri Eisin reiterated the international community's conditions, but did not make clear whether the deal would satisfy Israel. Israel would not have a more authoritative response before its weekly Cabinet meeting Sunday, she said.

Israeli Cabinet Minister Isaac Herzog told Army Radio that the government would read the agreement "with a magnifying glass" to see whether it met the international conditions.

British Foreign Secretary Margaret Beckett on Friday welcomed the "ongoing efforts to end the violence" but also said Britain would "need to study these proposals carefully and discuss them with our European and other partners."

At stake is roughly $1 billion a year in frozen aid from foreign donors in addition to approximately $500 million in withheld tax revenues collected by Israel on behalf of the Palestinians. The embargo has crippled the Palestinian government's ability to function, though the West and Israel have funneled millions of dollars through Abbas' office to prevent a complete collapse of the government.

French Foreign Minister Philippe Douste-Blazy said in Paris that inclusion of the term "respect ... is a step in the right direction, toward full adherence to the demands of the international community that we hold dear, including in particular the recognition of Israel."

Ahmed Youssef, a political adviser to Prime Minister Ismail Haniyeh of Hamas, said Saudi Arabia had promised the Palestinians $1 billion in aid -- which would mitigate the effects of the embargo -- but the donation could not be confirmed. Many Arab governments have failed to meet previous pledges of aid to the Palestinians.

Under the deal signed in the holy city of Mecca in Saudi Arabia, Haniyeh will remain prime minister and Hamas will get a total of nine portfolios, compared to six for Fatah. Nine other Cabinet posts will go to independents and smaller factions.

The vital post of interior minister, which would control the security forces, is to go to an independent, because Hamas and Fatah were each reluctant to see the other faction hold the ministry.

Young men danced to the beat of drums, carrying each other on their shoulders.

"Today is a feast," Maysra Balawi, 24, said late Thursday as he tried to steer his car through jammed streets. "It is the first happy protest I have seen in Gaza."

Hamas lawmaker Mushir al-Masri, speaking from Gaza, cautioned patience in celebrating the agreement.

It will be a great challenge to translate the agreement into reality on the ground and "to prevent those seeking to spoil the Palestinian unity," he said, without elaborating.

Signaling that thorny issues remain unresolved, al-Masri said a Hamas militia that has repeatedly clashed with security forces will not be disbanded.