Léonardo Santos Simão was in Abuja, Nigeria, on Sunday to participate in the extraordinary summit on the crisis, organized by regional bloc ECOWAS.
“He will continue his consultations with all partners with a view to restoring constitutional order and consolidating democratic gains in Niger,” said UN Deputy Spokesperson Farhan Haq, speaking in New York.
At the Abuja meeting, ECOWAS demanded the immediate release of Nigerien President Mohamed Bazoum, who was seized by some of his guards at his official residence on 26 July.
The bloc's 15 members said they would “take all measures necessary”, including use of force, if he is not reinstated in a week. They have also suspended commercial and financial transactions with Niger and closed air and land borders with the country.
Mr. Simão, who also heads the UN Office for West Africa and the Sahel (UNOWAS), condemned in the strongest possible terms the seizure of power by force and the undermining of democratic governance, peace and stability in Niger.
"The unconstitutional change of government in Niger has come to further complicate an already worsening security landscape in the Liptako Gourma area, and the region in general," he said.
He added that the UN Country Team in Niger is continuing its assistance to vulnerable people there.
He also reiterated the commitment of his office and the entire UN system to work closely with ECOWAS in support of the people of Niger.