A government source said she would be replaced by Defence Minister Alain Juppe, a heavyweight conservative who served as foreign minister and prime minister in the 1990s.
Alliot-Marie presented her resignation in a letter she hand-delivered to Sarkozy, a copy of which was seen by Reuters.
"I ask you to accept my resignation," the letter said.
France is under pressure to take the right approach to the pro-democracy movement sweeping through North Africa, including former French colonies where the political elite has had close ties with authoritarian rulers.
Sarkozy is expected to signal a new focus on foreign policy when he makes a hastily scheduled televised address later on Sunday. News on Saturday that he would make a speech fanned speculation he would announce another reshuffle of a cabinet he has tweaked several times since taking office in 2007.
The sources said the ruling UMP party`s leader in the Senate, Gerard Longuet, was likely to succeed Juppe as defence minister.
Sarkozy`s Chief of Staff Claude Gueant, his right-hand man, would be appointed interior minister, replacing Brice Hortefeux, who would become a presidential adviser.
Calls for Alliot-Marie to quit had grown louder in recent days following a series of blunders in her handling of the crisis in Tunisia, including taking a holiday there as protests raged. She accepted private plane rides from an associate of the now-ousted president Zine al-Abidine Ben Ali. (*)
Editor: Kunto Wibisono
Copyright © ANTARA 2011
