Vice-President Joe Biden made the call during a telephone conversation with his Egyptian counterpart Omar Suleiman.

It came after a day of renewed anti-government protests in Cairo and other Egyptian cities.

Correspondents said the demonstration in central Cairo was the biggest since the protests began on 25 January.

It came despite the government's announcement of its plans for a peaceful transfer of power.

President Hosni Mubarak has said he will stay in office until elections in September, when he plans to step down.

In remarks released by the White House, Mr Biden told Mr Suleiman that the transition to a more broadly based government should produce "immediate, irreversible" progress.

He also said the Egyptian interior ministry should immediately stop arresting and beating journalists and activists, and allow freedom of assembly and expression.

AP