Egypt's Foreign Minister Mohammed al-Orabi has resigned ahead of an expected major cabinet reshuffle.
Caretaker Prime Minister Essam Sharaf has promised a major shake-up of his administration amid continuing protests about the slow progress of reform.
Mass demonstrations began in January and led President Hosni Mubarak to resign after nearly 30 years in power.
Mr Orabi, who served as a diplomat under Mr Mubarak, has been in his job less than a month.
He took over from Nabil al-Arabi, a popular minister who left the post to head the Arab League.
Mr Orabi said he had submitted his resignation "to spare the prime minister any embarrassment during the current negotiations on the ministerial changes", Egypt's state-run Mena quoted him as saying.
Mr Sharaf reportedly announced that he had accepted the resignation on the social networking site Facebook.
Mr Sharaf, who has limited powers under the new military rulers of the country, has come under increasing pressure to speed up reforms.
"I am working hard to achieve your aspirations," AFP quoted him as saying in a Facebook posting.
Last week, almost 700 senior police officers were removed from their jobs over the killing of protesters during the revolution.
More than 800 protesters were killed during the 18-day revolt.
Protesters, some of whom have been holding an ongoing protest in Cairo's central Tahrir Square for more than a week, want a new government, limited power for the military council, the release of civilians being tried in military tribunals, and speedy public trials for former regime officials.