*Egyptian President Hosni Mubarak is about to speak in the next 10 to 15 minutes – and CNN is reporting that he is expected to announce that he will not seek re-election, according to a senior Obama administration.

More than a quarter-million people flooded Cairo’s main square Tuesday in a stunning and jubilant array of young and old, urban poor and middle class professionals, mounting by far the largest protest yet in a week of unrelenting demands for President Mubarak to leave after nearly 30 years in power.

According to The Guardian, one million protesters gathered at Tahrir Square. One Al Jazeera correspondent said two million attended the protests in the square and its surrounding areas.

The crowds – determined but peaceful – filled Tahrir, or Liberation, Square and spilled into nearby streets, among them people defying a government transportation shutdown to make their way from rural provinces.

Mubarak, 82, would be the second Arab leader pushed from office by a popular uprising in the history of the modern Middle East, following the ouster last month of Tunisia’s president.

Egyptian President Hosni Mubarak

The movement to drive Mubarak out has been built on the work of on-line activists and 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 Tunisia unrest took to the streets on Jan. 25 and mounted a once-unimaginable series of protests across this nation of 80 million people – the region’s most populous country.

The protests that have spread through parts of the Arab world also led to dramatic change in another country Tuesday, as Jordan’s king dismissed his government.

King Abdullah II made the decision following protests in recent weeks in which several thousand people demanded economic and political reforms.

Experts on the region said Tuesday Abdullah’s decision was aimed at warding off larger-scale demonstrations in the wake of Tunisia and Egypt.

The protests — which have also caught on to various extents in Algeria, Yemen, and Sudan — have proved to be “a real watershed event for the Arab world,” said Blake Hounshell, managing editor of Foreign Policy magazine. “It’s really unprecedented.”