The Economic Community of West African States has imposed sanctions on Niger after troops ousted President Mohamed Bazoum in a coup on July 26 and the bloc threatened military intervention as a last resort if talks fail to restore civilian rule.
In a statement on Thursday, the bloc insisted it wanted Bazoum back in power right away.
"The military authorities in Niger must restore constitutional order immediately by liberating and reinstating... President Mohamed Bazoum," it said.
Niger's new military leaders have dug in, saying they want a maximum three-year transition period to restore constitutional order and have ordered police to expel France's envoy as tensions build with a key partner in Niger's anti-jihadist fight.
Late on Thursday, Niger's interior ministry announced it was stopping UN agencies, NGOs and international organisations from working in military "operation zones".
It did not specify which regions were affected, but said the measures were "due to the current security situation".
"All activities and or movements in the zones of operations are temporarily suspended," it said.
Transition period
Tinubu said Nigeria returned to civilian rule in 1999 after a nine-month transition period instituted by former military head of state General Abdulsalami Abubakar, who has also headed delegations to meet the Niger junta.
"The president sees no reason why such cannot be replicated in Niger, if Niger's military authorities are sincere," the Nigerian presidency said in a statement.
Algeria, Niger's influential northern neighbour, has met with West Africa leaders in a bid to avoid any military intervention in Niger and has proposed a six-month transition.
But Tinubu's statement said there would be no relief from sanctions imposed by ECOWAS, of which he serves as chair, until the regime made "positive adjustments".
"The soldiers' action is unacceptable. The earlier they make positive adjustments, the quicker we will dial back the sanctions to alleviate the sufferings we are seeing in Niger," it said.
The overthrow of Niger's government has triggered concern around West Africa where Mali, Guinea and Burkina Faso have all been taken over by the military since 2020.
Fears of contagion have deepened with this week's military rebellion in Gabon to overthrow President Ali Bongo, toppled moments after being declared winner of a highly disputed weekend election.
Diplomatic battle
Niger's new military rulers have also been engaged in a political battle with Paris, and stripped France's ambassador of diplomatic immunity and ordered police to expel him, according to a letter seen Thursday by AFP.
The envoy "no longer enjoys the privileges and immunities attached to his status as member of the diplomatic personnel in the French embassy," according to their letter, dated Tuesday, to the foreign ministry in Paris.
Relations with France spiralled downwards after the July coup when Paris stood by Bazoum and refused to recognise Niger's new rulers.
Last Friday, the authorities gave French envoy Sylvain Itte 48 hours to leave the country.
France refused the demand, saying the military rulers had no legal right to make such an order.
French military spokesman Colonel Pierre Gaudilliere on Thursday warned that "the French military forces are ready to respond to any upturn in tension that could harm French diplomatic and military premises in Niger".
France has around 1,500 troops in Niger, many of them stationed at an airbase near the capital, to help fight a jihadist insurgency in Niger.
On August 3, Niger's new rulers denounced military agreements with France, a move that the government in Paris has also ignored on the grounds of legitimacy.
An organisation set up after the coup named the Patriotic Front for Niger Sovereignty (FPS) has led public demands for the coup leaders to take a hard line.
It is calling for a "massive" march next Saturday on the French base, followed by a sit-in until the troops leave.
Dispatch of troops
A landlocked former French colony in the heart of the Sahel, Niger is battling two jihadist insurgencies -- a spill over in southeastern Niger from a long-running conflict in neighbouring Nigeria, and an offensive in the southwest by militants crossing from Mali and Burkina Faso.
Bazoum came to office in 2021 after democratic elections -- a watershed in a country that had had no peaceful transition of power since independence from France in 1960.
He suffered two attempted coups before finally being toppled by members of his own guard.
ECOWAS responded by warning it could intervene militarily to restore civilian rule if efforts to end the crisis diplomatically fail.
Swift to support their military comrades in Niger, Mali and Burkina have said that any such operation would be deemed a "declaration of war" against them.
Burkina Faso has approved a draft law authorising the dispatch of troops to Niger, according to a government statement in Ouagadougou on Thursday.
AFP