Egyptian protesters are holding huge rallies in Cairo and other cities as they step up their efforts to force President Hosni Mubarak from power.
Organisers have been hoping to bring one million people on to the streets of the capital. The demonstration is the biggest since the protests began.
The atmosphere has been festive, with protesters singing and chanting.
State TV said Mr Mubarak was preparing to make a statement. Earlier he held talks with a senior US official.
Frank Wisner, a former ambassador to Egypt sent to Cairo on Monday, advised the president not to seek re-election in September or put forward his son Gamal as a candidate for president, senior US officials said.
The BBC's Kim Ghattas in Washington says the US is waiting for an answer, which could come in his statement.
Protest leaders like Mohamed ElBaradei say Mr Mubarak should step down by Friday at the latest.
"They hope that this will end today or Friday at the latest, and they called the coming Friday 'the Friday of departure', but I hope that President Mubarak will take heed before then and leave the country after 30 years of rule and give the people a chance, and I don't expect that he wants to see more blood," Mr ElBaradei told al-Arabiya TV.
BBC correspondents in Cairo's Tahrir Square say the crowds there have been much bigger than on the previous seven days of protests.
Journalists at the scene estimated that hundreds of thousands of people - men, women and children from a cross-section of Egyptian society - were there, although in the absence of official estimates, there is no way of finding out the exact numbers.
The BBC's Jim Muir says that hours after dusk and despite a theoretical 1500 (1300 GMT) curfew and bitter cold the square is still full of people.
Egypt's powerful army has vowed it will not use force against the protesters.
Many carried placards and banners daubed with anti-Mubarak slogans. Earlier, crowds cheered as an effigy of the president was hung from a set of traffic lights in the square.
But the BBC's John Simpson in the square says the demonstration has not been the critical moment people thought it would be, and it has not reached a tipping point.
There is a danger that the demonstrators could lose the initiative if a march to the presidential palace planned for Friday fails to budge Mr Mubarak, but it is hard to see how he can continue in power, he adds.
Meanwhile, new Vice-President Omar Suleiman said he would hold cross-party talks on constitutional reform.
Mr Mubarak reshuffled his cabinet on Monday to try to head off the protests, replacing the widely despised Interior Minister Habib al-Adly.
Prime Minister Ahmad Shafiq told state TV the new government would ensure bread supplies, tackle security problems and "review our entire political, constitutional and legislative situation, into something more satisfactory and appropriate for us as Egyptian citizens".
"Everything is subject to amendments, without limits," he said.
But analysts say the army's statement has been a major blow for President Mubarak, and appears to have encouraged protesters, who are flocking to central Cairo in their thousands.
The UN human rights chief, Navi Pillay, says 300 people may have been killed across the country since the protests began a week ago. They followed an internet campaign and were partly inspired by the ousting of President Zine al-Abidine Ben Ali in Tunisia last month.
Egypt has since cut off the internet in the country and text messaging services have been disrupted.
In other developments:
- The US state department announced it had ordered all non-emergency US embassy and government personnel to leave Egypt
- AFP news agency reported that US Ambassador Margaret Scobey had spoken by phone to Mr ElBaradei
- In an opinion piece for the New York Times, US Senate Foreign Affairs Committee head John Kerry called on Mr Mubarak to step down and engineer a peaceful transition
In Egypt's second biggest city, Alexandria, thousands of people have gathered to call for the president to step down.
Thousands more were out in the streets in Suez, and the Associated Press news agency reported protests in Mansoura, north of Cairo, and the southern cities of Assiut and Luxor.
With limited bus, train and internal flight services, access to the capital has been restricted.
Unnamed security officials were reported as saying all roads and public transportation to Cairo had been shut down.
Some protesters camped out in Tahrir Square on Monday night, saying they would stay there until Mr Mubarak's 30-year rule ended.
One demonstrator, Tarek Shalabi, told the BBC that groups were camped out in tents or sleeping out in the square, and described the atmosphere as "overwhelming".
"We're here because we want to make a statement. We're not going until Mubarak steps down," he said.
He said a stage had been set up where people could go up and make speeches, read out poetry or sing or chant political slogans.
Meanwhile, crowds of pro-Mubarak demonstrators held counter-protests elsewhere in the capital, raising fears of possible confrontations between the different groups.
On Monday, the Egyptian army said it respected the "legitimate rights of the people".
In its statement, carried on Egyptian media, the military said: "To the great people of Egypt, your armed forces, acknowledging the legitimate rights of the people... have not and will not use force against the Egyptian people."
Correspondents say the announcement is absolutely critical because it takes away a huge measure of uncertainty from the mind of any potential demonstrator.
A coalition of political opposition groups - incorporating the Muslim Brotherhood, political parties such as that led by Mr ElBaradei, and other prominent figures - has reportedly met, and told the Egyptian government that it will begin talks on its demands only after Mr Mubarak has stood down.
Concerns have also grown about the economy, as global oil prices on Monday topped $100 (£62) a barrel amid fears over the ongoing unrest.