The African Union (AU) has suspended Mauritania's membership in protest at the coup there on Wednesday, saying it must restore "constitutional order".
Deposed President Taya has not commented on the coup
Ministers will travel to the capital, Nouakchott, to inform the coup leaders officially of the AU's position.
The new regime meanwhile announced the dissolution of parliament in a statement broadcast on state radio.
Army officers overthrew President Maaouiya Ould Sid Ahmed Taya in a bloodless revolt on Wednesday.
Their action has been condemned by the United Nations, United States and France.
On Thursday, the new regime announced it would maintain the 1991 constitution, adding it would be "supplemented by a Military Council charter".
Under AU rules, a country is automatically suspended if it brings about unconstitutional changes.
The new rulers announced that the "Military Council for Justice and Democracy" would stay in power for up to two years, and would meanwhile organise free and fair elections.
They pledged to respect all international treaties and accords involving Mauritania.
The capital is calm, with people returning to work, traffic flowing and fewer soldiers on the streets than on Wednesday.
The council named security chief Colonel Ely Ould Mohammed Vall as the new leader.
Mr Vall has met the French and US ambassadors but details of their discussions have not been made public.
The Mauritanian army said it had ended the "totalitarian regime" of President Taya.
There are no reports of any casualties during the takeover.
The airport has now reopened.
Col Vall, 55, has been director of national security since 1987 and, after playing a key role in the 1984 coup which brought Mr Taya to power, had been seen as one of the president's closest aides.
There were street celebrations in Nouakchott following the announcement on national radio.
President Taya was returning from the funeral of King Fahd in Saudi Arabia when the coup took place. He is now in Niger.
President Taya took power in a bloodless coup in December 1984 and has been re-elected three times since.
Correspondents say he later made enemies among Islamists in the country, which is an Islamic republic.
Critics accuse the government of using the US-led war on terror to crack down on Islamic opponents.
Mr Taya had also prompted widespread opposition by establishing links with Israel, making Mauritania one of only three Arab states to have done so.
Last year nearly 200 people, including former President Mohamed Khouna Ould Haidallah, were put on trial for a series of alleged coup plots.