Egyptian President Hosni Mubarak's tottering regime is bracing for the toughest challenge yet as thousands of protesters demanding his ouster barreled towards main city centers on Tuesday as part of the planned March of a Million.

A Wall Street Journal report said on Tuesday Mubarak has made an offer to negotiate with the opposition groups on reform, his first such gesture ever since the protest started.

However, with the U.S. support waning and the military making a retreat, saying it understands the legitimacy of the people's demands, the countdown for the regime's end has apparently started.

The symbolism of the rising waves of civilian protest could not be missed on Tuesday as the embattled president appeared to lose more ground under his feet. With the White House support for Mubarak undergoing a sea change in recent days it looked more certain that he would not stay in power for too long. Though the U.S. has just stopped short of calling for his removal from power, it is no longer actively supporting him either.

In private, officials across the administration continued calling contacts in the Egyptian government, military and opposition to urge movement toward a transitional process leading to free elections, the Washington Post reported.

While Cairo's Tahir Square swelled with the largest number of protesters on record so far on Tuesday morning, another million-strong crowd was gathering in the Mediterranean port city of Alexandria, according to reports.

The growing army of civilian protesters reached protest venues despite the cancellation of train services in order to block people from congregating in cities. EgyptAir, the state-owned national carrier, has also announced it will stop services during curfew hours. However, the Cairo airport witnessed a scene of commotion as thousands of foreign nationals made a beeline for exiting the troubled country.

The numbers are certainly larger than we've seen over the last couple of days. A lot of people I've spoken to have said they will be attending, despite reports that there is the possibility that it could turn violent, an Al Jazeera correspondent reported from Cairo. The mood and atmosphere is incredible. People are thronging to the square in their hundreds, according to the reporter.

The push for democracy seems to have attained an unstoppable momentum at this point as reports said people belonging to all groups irrespective of age or societal status, are thronging the Tahir square and other venues despite fears the showdown with the hated government could turn violent.

However, contrary to reports on Sunday the Egyptian army was unlikely to open fire on demonstrators as long as the protest was peaceful. In a significant development the army said on Monday it would assure the right of freedom of expression to the great people of Egypt.

Mubarak swore in a new cabinet on Monday in an effort to take the sting out of the protesters' demands but that has had little effect. Protesters have made it amply clear they will be satisfied only with Mubarak's exit.

We have no plans to reach out to Mubarak because in our eyes he is already gone and his regime is a failure, the WSJ quoted Shadi Taha, the deputy head of the Al Ghad Party, as saying.

Meanwhile, the interior ministry stuck to its position that only 78 people have died in clashes with the police though the protesters maintain several more have lost their lives since the protests erupted last week.