Foreign Secretary William Hague has warned that Egypt is in danger of falling into the hands of extremists as tensions in the country build.
The military have been staging a show of strength on the sixth day of mass demonstrations calling for the end of President Hosni Mubarak's three-decade rule.
But protesters show no sign of giving way despite more than a hundred deaths so far, with huge crowds again roaming the streets of major cities.
US Secretary of State Hillary Clinton delivered the strongest hint yet that Washington does not expect its former ally to cling on to power, calling for an "orderly transition" to democracy.
"We want to see an orderly transition so that no-one fills a void, that there not be a void, that there be a well thought-out plan that will bring about a democratic participatory government," Mrs Clinton said in a round of broadcast interviews.
Mr Hague stressed that Egypt was a "sovereign nation" and Britain was not trying to "pick who should be president".
But he said there had to be a shift to an "open and democratic society".
"What matters is that the process takes place, whatever that means for President Mubarak personally, whatever he judges that means for him personally," the Foreign Secretary said.
"It is important for him to initiate that transformation and that broadly based government, and that is what we would like to see.
"That is far preferable of course to Egypt falling into the hands of extremism or a more authoritarian system of government."
