West African leaders scheduled a summit for Thursday to discuss the Niger junta’s rejection of an ultimatum to reinstate the ousted president, as the United States sent a top official to Niamey to push for a return to democracy.

The Economic Community of West African States (ECOWAS) had told leaders of the July 26 coup to stand down by Sunday or face a possible military intervention.

But the junta, under self-declared head of state General Abdourahamane Tiani, former commander of Niger’s presidential guard, instead closed the airspace and pledged to defend the country.

The bloc has not directly responded but said on Monday it would hold the Thursday summit to discuss the standoff, a decision the European Union and United States said allowed more time for mediation.

U.S. Acting Deputy Secretary of State Victoria Nuland flew to Niger’s capital Niamey on Monday for “frank and difficult” talks with senior junta officials, who rebuffed calls for a return to democratic order.

“They are quite firm in their view of how they want to proceed, and it does not comport with the Constitution of Niger,” she told reporters late on Monday by phone before leaving Niamey.

“It was difficult today and I will be straight up about that.”

Niger’s uranium and oil reserves and its pivotal role in a war with Islamist militants in the Sahel region give it economic and strategic importance for the United States, Europe, China and Russia.

Coup leaders in Niamey have struck a defiant tone, repeatedly affirming their resolution to stand firm and fight if necessary. The junta has cited persistent insecurity as its main justification for seizing power, but data on attacks shows security had actually been improving.

In a further sign of its will to remain in power, the junta on Monday named former Finance Minister Ali Mahamane Lamine Zeine as the new prime minister.

Coup leaders have also called on young Nigeriens to be ready to defend the country – a rallying call that several students at the capital’s Abdou Moumouni university said on Monday they would heed.

“No sacrifice is too much … for our country. We are ready to give our lives,” said economics masters student Soumaila Hamadou on the rain-drenched campus.

Niamey appeared calm on Monday with people going about their business as usual, but the closure of Nigerien airspace disrupted the skies.

Landlocked Niger is more than twice the size of France and many flight paths across Africa would normally pass above it. Air France suspended flights to and from Ouagadougou in Burkina Faso and Bamako in Mali, which both border Niger, until Aug. 11 and warned that some flight times would increase.

ECOWAS has taken a harder stance on the Niger coup, the region’s seventh in three years, than it did on previous ones. The credibility of the 15-nation club is at stake because it had said it would tolerate no further such overthrows.

ECOWAS defence chiefs agreed on Friday on a possible military action plan if the detained president, Mohamed Bazoum, was not released and reinstated, although they said operational decisions would be decided by heads of states.

But the bloc’s unity has been broken by a promise from the ruling juntas in Mali and Burkina Faso, both member states, to come to Niger’s defence if needed.

Both countries sent delegations to Niamey to show solidarity, the Malian army said on social media on Monday. Later, a representative of the Malian delegation reiterated his country’s backing for the junta.

A fracture within ECOWAS and escalation of the stand-off with Niger would further destabilise one of the world’s poorest regions, already facing a hunger crisis and an Islamist insurgency that has killed thousands and displaced millions.

The threat of worsening security has prompted France to warn its citizens against all travel to Niger, while the Chinese Embassy in Niamey said its nationals in Niger should leave for a third country or return home if they had no reason to stay.

HOPE FOR DIPLOMACY

African and Western allies have imposed sanctions and cut aid to Niger to pressure the junta to step down.

Earlier on Monday, the U.S. State Department said “hundreds of millions of dollars” in paused U.S. assistance was at stake if the country’s junta did not reinstate the elected government.

Despite these looming hardships, coup organisers appear to enjoy support from at least part of the population.

A pro-coup rally drew thousands of people to a Niamey stadium on Sunday, while some locals, including women, have picketed intersections in the capital to offer non-violent resistance in support of the junta if needed.

“This proves the commitment and determination of Niger’s young women to accompany and support them (the junta),” said Zeinabou Boubacar Zakou, a student and member of the Nigerien Young Women’s Council.