After two days of street battles between opposing factions in Cairo, undaunted throngs crowded Tahrir Square after prayers on Friday, showing resilience and determination that ratcheted up pressure on embattled President Hosni Mubarak to step down.

As the crowd swelled to around 100,000, reports surfaced that White House staff were in talks with Egyptian officials about a power transition ahead of free elections later this year.

In Washington, U.S. President Barack Obama said that a "transition period" should begin now that would see Mubarak's three-decade rule come to an end.

"We want to see this moment of turmoil turned into a moment of opportunity," Obama said.

Though Obama stopped short of directly calling on Mubarak to step down, there is a strong belief among top officials that the crisis will only be exacerbated if the Egyptian president clings to power.

Still, there is concern about a timeline for the transition.

Nobel Peace laureate Mohamed ElBaradei, a key figure in the protests, said that the government's previously-stated five-month plan to redraw the nation's constitution and hold presidential elections is too rushed.

Instead, he is pushing for a year-long mandate under a transitional government, which would allow the country to sufficiently prepare for democracy. In the past, opposition groups have been stamped out and elections have essentially been one-candidate votes.

"People are not stupid ... This is not really a genuine desire to go for reform," ElBaradei said, criticizing the government's plan.

Earlier in the day, watching developments in the Egyptian capital, CTV's Middle East Bureau Chief Martin Seemungal said that a massive security cordon was screening anyone trying to get into the square.

In addition, protesters had set up their checkpoints inside the military's cordon to search bags and scrutinize the IDs of people entering the square.

The result, CTV's Lisa LaFlamme said after spending several hours in the square Friday morning, was a truly diverse cross-section of Egyptian society.

"I've spoken to grandmothers, fathers, little children inside that square," LaFlamme said.

"Inside that square it is a great cross-section of people from this country who just want better for themselves and they feel that if Mubarak steps down -- that will be the beginning of a new day here."

Organizers hopeful this might be the last of more than 10 days of pitched protest dubbed Friday's rally a "day of departure."

Mubarak has said he will step down, but in an interview with ABC News said he was worried leaving before the end of the remaining seven months of his term would plunge the country into chaos.

U.S. officials have indicated Mubarak's immediate resignation and the creation of a military-backed caretaker government is indeed among several proposals now on the table in talks between Egypt and the White House.

While ElBaradei has said he is not interested in contesting the presidency, another self-professed candidate was warmly welcomed when he visited Tahrir Square on Friday.

Arab League chief Amr Moussa was greeted with chants of "we want you as president, we want you as president," when the former Egyptian foreign minister appeared with his entourage.

In an earlier interview with France's Europe 1 radio, Moussa said, "Why say no?" when asked if he would consider a role in a transitional government or, ultimately, the presidency.

As the political chips fall, there are other signs Egyptian officials are softening.

Amid the simmering discontent Friday, Egyptian Defence Minister Hussein Tantawi became the highest-level government official to visit Tahrir Square since the uprising began. And on Thursday, Egypt's Vice President Omar Suleiman said he had invited the outlawed opposition group Muslim Brotherhood to participate in talks if and when they begin.

Suleiman, who ElBaradei has said could play a role in a transitional government, said issues up for negotiation could include provisions to ensure independent supervision of elections, an easing of the rules determining who can seek the presidency and a term limit for the country's top job.

A new committee composed of various factions including former presidential candidate Ayman Nour has been formed to conduct any negotiations on the protesters' behalf, but it says it will not enter transition talks until Mubarak leaves office.

With files from The Associated Press