The European Union has suspended all activities with Niger, including financial assistance, and civilian and security cooperation.
The European Union said there was still room for mediation efforts in Niger, which has been grappling with uncertainty since mutinous soldiers led a coup on 26 July.
ADVERTISEMENT"We are not working together with the current illegitimate authorities in Niger," said European Commission spokesperson Peter Stano, speaking on Tuesday at a news conference in Brussels.
Regional tensions have mounted since the coup nearly two weeks ago when mutinous soldiers detained President Mohamed Bazoum and installed former presidential guard head Abdourahamane Tchiani as head of state.
"There will be no positive consequences if this military coup is allowed to proceed," Stano warned.
"We still believe that there is a space, there is a room for mediation efforts. So we will not go beyond and speculate," Stano added.
Nigeriens are facing deepening uncertainty about whether a regional bloc will follow through on its threat to use military force to try to reinstall the ousted president or if last-minute diplomacy will prevail.
New Prime Minister
An economist and former government minister has been selected to be the new prime minister by coup leaders in Niamey.
Niger's military coup leaders announced the appointment of Ali Mahaman Lamine Zeine as prime minister on Monday evening in a statement read out on national television, at a time when the international community is seeking to restore constitutional order.
"Mr (Ali Mahaman) Lamine Zeine has been appointed Prime Minister", Colonel Major Amadou Abdramane reported.
"Lieutenant-Colonel Habibou Assoumane" has also been "appointed Commander of the Presidential Guard", added Mr Abdramane.
ECOWAS ultimatum
These appointments come a day after the Economic Community of West African States (ECOWAS) gave the ruling military an ultimatum to restore President Mohamed Bazoum to office. The organisation did not rule out the use of force if this demand was not met.
Niger's Western and African partners are divided on the question of military intervention to return power to civilians, before ECOWAS meets again on Thursday in Abuja, Nigeria.
On Tuesday AFP reported it had seen a letter from the coup’s leaders to ECOWAS, postponing the visit of a delegation to Niamey on security grounds.
President Bazoum
President Bazoum has remained sequestered in his private residence since the day of the coup.
Ali Mahaman Lamine Zeine, an economist by training, has held ministerial positions in previous governments in Niger and was also a resident representative of the African Development Bank (AfDB) in Chad, Côte d'Ivoire and Gabon.
Born in 1965 in Zinder South, Niger's second most populous town, he joined the Ministry of Economy and Finance in 1991 after studying at the Ecole Nationale d'Administration (ENA) in Niamey. He is also a graduate of the Centre d'Etudes Financières, Economiques et Bancaires in Marseille and Paris.