Senegal has said it would be prepared to send troops into Niger if regional bloc Ecowas decided to do so.
At the weekend, Ecowas heads of state threatened the use of force if elected-President Mohamed Bazoum is not reinstated by next Sunday. He was overthrown in a military coup last week.
Ecowas has also imposed economic sanctions.
Niger is the fourth country in the region to have experienced a coup since 2020.
Senegal’s Foreign Minister Aissata Tall Sall told reporters that there had been “one coup too many” in the region, the AFP news agency quotes her as saying.
“Senegalese soldiers, for all these reasons, will go there,” she added.
Meanwhile, thousands of people have demonstrated in Niamey, Niger’s capital, to show their support for the junta.
A coalition of civil society organisations opposed to the French military presence in the country called the protest.
Correspondents say there are also many people in Niger who are opposed to the coup.