* Election win strengthens Islamists' hand against generals
* Muslim Brotherhood to take pragmatic approach
* Democracy in Arab world favours Islamists, for now
By Alistair Lyon
CAIRO, Dec 3 (Reuters) - Egyptian voters are sweeping Islamists to a victory that sidelines liberals and sets up a struggle with army generals eager to keep their power despite the fall of Hosni Mubarak.
The Islamists won't have it all their way. They are split into two main factions. If they push a religious agenda too hard, they risk alienating the many floating voters who decided to give them a chance.
And the military men who have ruled Egypt for six decades will not easily relinquish their grip.
The outcome of the polls may not be welcome to the West, or to many of the young protesters who overthrew Egypt's ruler of 30 years, but it confirms a trend set by Islamist election wins in post-uprisingTunisia and Morocco in the last two months.
"It does have implications for U.S. and Western interests in the region. It's not going to be business as usual," said Shadi Hamid, director of research at the Brookings Doha Center.
"But it's not a specifically Islamist issue. Arabs don't like U.S. policy, so the governments they elect will not like U.S. policy. It's just a new reality in the region."
Armed with popular legitimacy from Egypt's freest vote since army officers ousted the king in 1952, theMuslim Brotherhood and ultra-conservative Salafi Islamists look set to dominate parliament once a tortuous voting process winds up in January.
"Egyptian voters had three choices: the remnants of the Mubarak regime, an Islamist current that had been its strongest opponents and new groups that started establishing themselves after the revolution," said Adel Soliman, head of Cairo's International Centre for Future and Strategic Studies.
"They rejected the first choice and the new groups were not crystallised yet, so Islamists became their only option."
The Brotherhood, closer to political power than at any time since its founding in 1928, has told "all those who associate themselves with democracy to respect the will of the people".
"NO DIPLOMATIC FIRESTORM"
Yet a movement seasoned by decades of patient grass-roots work is unlikely to rush to impose purist Islamic codes, tear up Egypt's peace treaty with Israel or confront Washington, still the source of $1.3 billion a year in military aid.
"We are talking about pragmatic politicians. They don't want a breach with the United States or Europe. They don't want a diplomatic firestorm," Hamid said, citing informal contacts between the Brotherhood and U.S. officials in recent months.
But the Nov. 28-29 election and the bloody protests against army rule that preceded it have shaken up what Egyptian military analyst Safwat Zayat described as a tacit U.S.-approved deal between the Brotherhood and the ruling military council, which had envisaged a transfer to civilian rule perhaps in 2013.
"The Tahrir protests were central to forcing the council to back off and set a date for transferring power in early July," he said, referring to demonstrations in Cairo's Tahrir Square and elsewhere in which 42 people were killed and 2,000 wounded.
Zayat said the army had regained some credit for running a generally free election, but the vote itself had weakened its chances of embedding itself as Egypt's ultimate arbiter.
"The military power will not be able to go beyond its current role or enshrine its role in the constitution," Zayat said. "The Brotherhood is now stronger than before because it has voting power. The armycannot co-opt it now that it has legitimacy in parliament. The relationship has changed."
First-round election projections show the Brotherhood's Freedom and Justice Party (FJP) gaining some 40 percent of the vote, with a surprisingly strong 20 percent for the Salafi al-Nour Party and up to 20 percent for the liberal Egyptian Bloc.
The FJP has indicated it will not ally with the Salafis, preferring liberal coalition partners to share the task of dealing with Egypt's crippling economic crisis and to reassure Egyptians and outsiders nervous about Islamist intentions.
ASSERTIVE PARLIAMENT
Soliman said the FJP might have to moderate and broaden its discourse even for the remaining stages of the election.
"They will have to present themselves more as a civil force focusing on democracy and freedoms, because those who voted for them aren't devoted followers and might change their minds."
For now, the military council remains in charge and its appointee, Kamal al-Ganzouri, is forming a new government.
But the next parliament will want a major voice in shaping a new constitution that is supposed to be drawn up and put to a referendum before a promised presidential election in June.
A now-defunct proposal floated by the military-appointed government in the run-up to the election set out supra-constitutional principles that would have shielded the army from civilian control and given it a strong role in writing the constitution.
That prompted Islamist protests against army rule, which in turn ignited last month's street confrontations around Tahrir.
"This is going to be a strong and assertive parliament and one that challenges the military's hold on politics," Hamid said, adding one flashpoint would be the Brotherhood's ambition to turn Egypt into a parliamentary system instead of the presidential one favoured by the army and some liberals.
"One worry is that the liberals will gravitate toward the army over a common fear of the Islamists," he said. "That would not be good for Egyptian democracy and it would undermine the democratic credentials of liberals in Egypt."
Hamid said shaken liberals should give Islamists a crack at government, knowing that the dire economic outlook means they will "inevitably fail to deliver on people's expectations".
The economic crunch may also put the military under more pressure to open up its budget and business enterprises to public scrutiny, something the generals will fiercely resist.
The Brotherhood, ever pragmatic, may still be willing to let the generals play an important role behind the scenes.
"If it's in the Brotherhood's interest, it will come to an understanding with the military," Hamid said. "Is that going to be enough for the military or will it want more? (Additional reporting by Marwa Awad and Tamim Elyan; Editing by Alessandra Rizzo)