The junta also claimed that two central African countries are preparing for an invasion, but did not say which ones, and called on the country's population to defend it.

The junta said any attempt to fly over the country will be met with "an energetic and immediate response." International airlines have begun to divert flights around the airspace of Niger, which the United States and others had seen as the last major counterterrorism partner in the vast Sahel region, south of the Sahara Desert, where groups linked to al-Qaida and the Islamic State group are expanding their influence.

In Mali, the armed forces said today that it and Burkina Faso, both neighbours of Niger run by military juntas, were sending a delegation of officials to Niger to show support. Both countries have said they would consider any intervention in Niger as a "declaration of war" against them.

Regional tensions have mounted since Niger's coup nearly two weeks ago, with the mutinous soldiers detaining Bazoum and installing Gen. Abdourahmane Tchiani, former head of the presidential guard, as head of state. Analysts say the coup is believed to have been triggered by a power struggle between Tchiani and the president, who was about to fire him. It was not immediately clear what ECOWAS will do now that Sunday's deadline has passed. The region is divided on a course of action. There was no sign of military forces gathering at Niger's border with Nigeria, the likely entry point by land.

On Saturday, Nigeria's Senate pushed back on the plan to invade, urging Nigeria's president, the bloc's current chair, to explore options other than the use of force. ECOWAS can still move ahead, as final decisions are made by consensus by member states. A former British army officer who worked in Nigeria said military officials there told him Monday that President Bolu Tinubu had not given orders to use military force. He spoke on condition of anonymity because of the sensitivity of the situation.