The West African bloc has angered Niger after it postponed its negotiation mission to the country because of "technical problems" with the plane that was supposed to take most of the delegation from the Nigerian capital, Abuja to Niamey.
The prime minister appointed by Niger's military regime criticised Ecowas - an alliance of West African countries - for "bad faith" after only Togo attended.
A statement from Ecowas explained that their absence was not meant as a snub to the military-led country, but rather because of "technical problems with the aircraft the commission had chartered for the flight from Abuja to Niamey".
The West African bloc said it would reschedule the mission as soon as possible.
Ecowas has imposed tough sanctions on Niger since a coup toppled President Mohamed Bazoum last July.
It has demanded the release of President Bazoum several times since he was put under house arrest.
The bloc has also threatened military intervention and suspended all trade ties to the landlocked country.
Niger's junta hoped the meeting would help ease diplomatic relations with the Ecowas countries.