The proposed law, which would replace a constitution dating to 1991, has won the approval of most politicians and civic and political rights groups.

It would be the first in a series of democratic reforms that the military junta, which rose to power in a bloodless coup in August, wants to introduce in an attempt to put to an end to "more than 20 years of despotic rule."

The amendments to the old constitution - result of talks between parties, civil groups and government in October - limit the length of presidencies to two terms of five years and set a maximum age of 75 for a president.

Presidents have been able to serve a six-year term of office, renewable indefinitely.

Former president Maaouiya Ould Taya had ruled the country since a December 1984 coup d'etat. He was then re-elected three times.

Constitution protected

It would be mandatory under the new constitution for future heads of state to take an oath not to revise or back any efforts to change the law with respect to presidential terms.

The military took power while
Taya was out of the country

The junta says the proposed constitution would form the backbone of political reforms because it would "guarantee the peaceful and democratic changeover of power."

Two small parties, the Alliance for Justice and Democracy and the Party for the Third Generation, and an exiled group campaigning for the rights of black Mauritanians, the African Liberation Forces of Mauritania, have called for a boycott of the vote.

They argue that the new constitution ignores issues of "cohabitation between the different national communities", such as Arabs and black Africans, and does not address the issue of slavery, which was officially abolished in 1981 but is still practised in parts of the country, according to rights activists.

Black and white Moors make up more than 80% of the population of the former French colony, while black Africans are 18%.

The government said more than 984,000 of the country's 2.8 million people have been registered to vote.

Municipal and legislative elections are planned in November and polls in 2007 will elect members of the upper house and a president.

Members of the ruling Military Council for Justice and Democracy have promised not to take part in the elections and to step down once the transition process is over.