Nuland said she warned Niger against following neighbouring Mali in bringing in Russia's Wagner mercenaries.

A senior US diplomat traveled to Niger on Monday, where she had "frank" and "difficult" talks with the leaders of the military coup.

"They are quite firm in their view on how they want to proceed, and it does not comport with the constitution of Niger," Acting Deputy Secretary of State and Under Secretary for Political Affairs Victoria Nuland told reporters during a teleconference.

"We kept open the door to continue talking. But again, it was difficult today, and I will be straight up about that," she said.

Nuland said Secretary of State Antony Blinken asked her to make the trip to Niger while she was in Jeddah, Saudi Arabia to attend peace talks on Ukraine.

The US "wanted to speak frankly to the people responsible to this challenge to the democratic order to see if we could try to resolve these issues diplomatically," she added.

She said she was also able to meet with a "broad cross-section" of Nigerien civil society, including "long-time friends" of the US, journalists and activists.

House arrest

Nuland also met with Moussa Salaou Barmou, the self-proclaimed chief of defense, and three colonels supporting him for “extremely frank and at times quite difficult” conversations, she said.

She said her requests to meet with President Mohamed Bazoum were denied.

"We’ve talked to him on the phone, but we haven’t seen him – and that was never granted," she said. "We also asked for some gestures of health and welfare; he is in a very difficult situation under virtual house arrest, along with his son and his wife."

"We also were not granted an opportunity to see the self-proclaimed president, Mr. (Abdourahmane) Tiani. So we were left to have to depend on Mr. Barmou to make clear, again, what is at stake," she said.

Meanwhile, the junta has appointed a transitional prime minister, according to a decree read on national television on Monday night. This comes more than a week after the military coup that toppled President Mohamed Bazoum.

The caretaker government, which calls itself the National Council for the Safeguarding of the Country, appointed economist Ali Mahamane Lamine Zeine.

New government

Zeine, 58, served as finance minister under Mamadou Tandja, who led the country from 1999 to 2010 when that government was toppled in a military coup.

Zeine currently serves as the African Development Bank’s Country Manager for Chad. He previously served at the same institution and position in Ivory Coast and Gabon. Zeine is is expected to lead consultations for the formation of a new government.

On July 26, a group of soldiers calling themselves the National Council for the Safeguarding of the Country seized power after detaining President Bazoum, saying they took the step due to the "deteriorating security situation and bad governance."

The Economic Community of West African States (ECOWAS), which consists of 15 countries, will hold another emergency summit on Thursday in the Nigerian capital Abuja to discuss the crisis.

TRT Afrika and agencies