Many of the hundreds of thousands of demonstrators in the centre of Cairo have greeted with derision President Mubarak's decision to step down only when his current term ends in September.
A leading opposition figure, Mohamed El-Baradei, dismissed it as "a trick" to try to cling on to power.
Protesters in the city's Tahrir Square told the BBC's Kevin Connolly that they were disappointed and angry at the president. "The game's not over," one said, while another insisted "we reject his proclamation, we will stay here until Mubarak goes out".
Speaking on the programme, the country's newly-appointed finance minister, Dr Samir Radwan, said that "chaos will take over" if President Mubarak quits now.
He insisted that the Egyptian government was "using every possible facility to help the peaceful transition to democracy" and that it was willing to speak to "all shades of political opinion", including the outlawed Muslim Brotherhood.
But Mr Radwan warned that "whoever stands in the way [of democratic reform] is out of the equation".
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