Anti-Mubarak reformists and opposition figures hoped one million Egyptians would join the biggest protest to mark an uprising which erupted a week ago to force Mubarak to step down.

The disintegration of Mubarak's power structure would usher in a new era in modern Egyptian history and reconfigure the geopolitical map of the Middle East, with huge ramifications for Washington and allies from Israel to oil giant Saudi Arabia.

The army, a powerful and respected force in Egypt, dealt a possibly fatal blow to the 82-year-old Mubarak on Monday night when it said troops would not open fire on protesters and that they had legitimate grievances and a right to peaceful protest.

Mubarak's new vice president, Omar Suleiman, appointed to show the government was willing to bring in reforms, offered to open a dialogue with the opposition.

But the measure, along with the dismissal of his cabinet and the promise of reform, appeared to be too little, too late.

"There is nothing that we will accept from him other than he takes the plane and leaves," said Ahmed Helmi, a 45-year-old lawyer, one of thousands of Egyptians flocking to Tahrir Square on Tuesday to try and to push Mubarak over the edge.

The uprising broke out eight days ago amongst a population fed up with corruption, oppression and economic hardship and quickly spiraled to a crisis unprecedented during 30 years of rule enforced by ruthless security forces.

The United States and other Western allies watched at first in confusion as thousands demanded the downfall of a stalwart ally who has been a key figure in Middle East peace moves.

As the crisis grew, Washington called for reforms and free elections but it is also concerned that Islamists could gain a slice of power should Mubarak be forced out.

Political analysts said it was now just a matter of time until Mubarak stepped down.

"The succession is already under way," said Steven Cook at the Council on Foreign Relations.

"The important thing now is to manage Mubarak's exit, which must be as graceful as possible at this point. For honor's sake, the brass won't have it any other way."

In Tahrir (Liberation) Square, which has become the focus of the protest movement, people poured in under the watch of soldiers backed by tanks and armored personnel carriers.