Malian coup leader Col Assimi Goita promised elections in February as he was sworn in as transitional president on Monday.
Col Goita also appointed a civilian prime minister after international anger against a second coup in Mali in nine months.
After the swearing-in, political veteran Choguel Maiga, 63, was announced as prime minister, an appointment that was expected.
Col Goita led the coup that toppled the country's democratically elected leader last August, and he removed the civilian president and prime minister of a transitional government on May 24.
In doing so, he sparked diplomatic uproar and deepened fears of chaos in a country that plays a leading role in stemming the insurgency sweeping the Sahel.
"I swear before God and the Malian people to preserve the republican regime ... to preserve democratic gains," he said during the ceremony in the capital, Bamako.
Dressed in full military regalia, Col Goita said Mali would fulfil its commitments, pledging "fair and transparent" elections by February next year.
It is unclear how Mali's partners and neighbours, who condemned the second coup, will respond.
It prompted the African Union and the Economic Community of West African States to suspend Mali, calling for the appointment of a civilian prime minister.
Economic community mediator Goodluck Jonathan, the former Nigerian president, is expected in Mali on Tuesday.
Former colonial power France suspended military co-operation with Malian forces and stopped giving military advice.
Mr Maiga, a leading figure in the opposition M5 movement, has been a presidential candidate three times.
He is regarded by Malian observers as a figure who could lend credibility to the post-coup administration.
The M5 helped to build dissent that led to the removal of former president Ibrahim Boubacar Keita last August after mass protests against corruption and the insurgency.
But the movement was sidelined in the first post-coup government, which was dominated by the military.
That government pledged to reform the constitution by October, and hold elections in February.
But M5 became a vocal critic, calling the transitional administration a "disguised military regime".
Since the May coup, however, there has been a rapprochement between M5 and the army.
Shortly afterward, Col Goita said he wanted to appoint an M5 figure as his prime minister, and the naming of a civilian fulfils a demand from the international community.
The Union for the Republic and Democracy party, the main opposition during Mr Keita's presidency, welcomed Mr Maiga's nomination and said it was ready to support the transitional government.
Bocary Treta, leader of the Rally for Mali, the party of the deposed president, called for transparent elections.
Maintaining its international partnerships, not least with France, is crucial for Mali. One of the world's poorest countries, its security forces lack equipment and training.
France has 5,100 troops in the Sahel to help fight violence that erupted in Mali in 2012 and now threatens the region.
By stressing that Mali would keep to its commitments, Col Goita appeared on Monday to be seeking to allay international concerns.
In a move that will reassure foreign partners, he also promised to continue work on the 2015 Algiers accord, an agreement between the central government and several armed groups.
The deal, which has never been fully implemented, is considered to be crucial to ending Mali's conflict.
But its future was put into question, however, when it became clear that Mr Maiga was poised to become the prime minister. As an opposition figure he was a vocal critic of the peace accord.
Other possible rifts loom.
Mr Maiga is close to religious leader Mahmoud Dicko, who has spoken in favour of negotiating with the extremists, a position fiercely opposed by France.
Col Goita alluded to such negotiations on Monday, saying during the ceremony that "inclusive national dialogue" will continue in a "judicious manner".
