For Groups Opposing Mubarak, a Fragile Coalition

Anti-government protests in Egypt built up Tuesday in an all-out push that opposition groups hoped would topple President Hosni Mubarak once and for all.

The national movement to oust the leader of nearly three decades has united diverse factions - but the coalition is fragile and the temporary unity masks deep divisions and historical mistrust that may quickly rise to the surface in the power vacuum that would likely follow Mubarak's fall.

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"After Mubarak goes … people shouldn't think that the problem is over," Richard Haass, president of Council on Foreign Relations told CBS' "The Early Show" Tuesday. "That's when the problem really begins."

The array of movements involved in the protests have sometimes conflicting agendas - including students, online activists, grass-roots organizers, old-school opposition politicians and the fundamentalist Muslim Brotherhood, along with everyday citizens drawn by the exhilaration of marching against the government.

The various protesters have little in common beyond the demand that Mubarak go. Perhaps the most significant tensions among them is between young secular activists and the Muslim Brotherhood, which wants to form a state governed by Islamic law but renounced violence in the 1970s unlike other Islamist groups that waged a violent campaign against the government in the 1980s and 1990s. The more secular are deeply suspicious the Brotherhood aims to co-opt what they contend is a spontaneous, popular movement. American officials have suggested they have similar fears.

"Clearly the religious radicals … [will] try to exploit any political openings, which is why it's important that sooner rather than later a dialogue starts to take place, Mubarak leaves office and order is restored and the economy gets started up again," Haas said. "The longer this plays out, the more things begin to unravel. … It creates political openings. And what we've learned through history is often not the first phase or even the second phase that matters - it's the third or fourth phase."

More than a quarter-million people flooded filled Tahrir, or Liberation, Square in Cairo Tuesday in by far the largest demonstration in a week of unceasing demands Mubarak's resignation.

Protesters streamed into, among them people defying a government transportation shutdown to make their way from rural provinces in the Nile Delta. The peaceful crowd was jammed in shoulder to shoulder - schoolteachers, farmers, unemployed university graduates, women in conservative headscarves and women in high heels, men in suits and working-class men in scuffed shoes.

They sang nationalist songs and chanted the anti-Mubarak "Leave! Leave! Leave!" as military helicopters buzzed overhead. Organizers said the aim was to intensify marches to get the president out of power by Friday, and similar demonstrations erupted in at least five other cities around Egypt.

The loosely organized and disparate movement to drive him out is fueled by deep frustration with an autocratic regime blamed for ignoring the needs of the poor and allowing corruption and official abuse to run rampant. After years of tight state control, protesters emboldened by the overthrow of Tunisia's president last month took to the streets on Jan. 25 and mounted a once-unimaginable, relentless series of protests across this nation of 80 million people - the region's most populous country and the center of Arabic-language film-making, music and literature.

The military promised on state TV Monday night that it would not fire on protesters answering a call for a million to demonstrate, and recognized the "legitimate demands by honorable citizens," a sign that army support for Mubarak may be unraveling as momentum builds for an extraordinary eruption of discontent and demands for democracy in the United States' most important Arab ally.

A second day of talks among opposition groups at the headquarters of the liberal Wafd party fell apart after many of the youth groups boycotted the meeting over charges that some of the traditional political parties have agreed to start a dialogue with Suleiman.

Nasser Abdel-Hamid, who represents pro-democracy advocate Mohamed ElBaradei, said: "We were supposed to hold talks today to finalize formation of a salvation front, but we decided to hold back after they are arranging meetings with Sulieman."

The U.S. State Department said that a retired senior diplomat - former ambassador to Egypt Frank Wisner - was now on the ground in Cairo and will meet Egyptian officials to urge them to embrace broad economic and political changes that can pave the way for free and fair elections.

ElBaradei, the former head of the U.N. nuclear watchdog, invigorated anti-Mubarak feeling with his return to Egypt last year, but the outlawed Muslim Brotherhood remains Egypt's largest opposition movement.

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In a nod to the suspicions, Brotherhood figures insist they are not seeking a leadership role.

The Brotherhood appeared to be caught flat-footed by the eruption of protests a week ago, fueled by young, more secular activists, and was slow to join in.

But once it did call out its membership, the result was that Alexandria, where the Brotherhood is centered, saw the largest protests - and the fiercest clashes with police - of any city in Egypt, with tens of thousands marching through the streets, a sign of its organizing prowess.

Still, though it can bring out the sheer numbers, the Brotherhood is reluctant to present itself overtly as a leader or driving force in the protests, realizing that storming out with its hard-line slogans of "Islam is the solution" would disillusion secular groups, raise panic that it is trying to take over and bring a harsher government crackdown.

Still, Brotherhood members appeared to be joining the protest in greater numbers and more openly. During the first few days of protests, the crowd in Tahrir Square was composed of mostly young men in jeans and T-shirts.

As soon as Mubarak does step down, "You're going to see the splintering," Haass said. "You're going to see the radical religious forces - who probably represent a quarter to a third of Egypt - they're going to go in one direction and all of the civilians [will go in another]. You're going to see all of the rivalries all the different agendas. And that's why this is a very dangerous situation."