"Our special envoy today had a first contact in which she expressed clearly our position to the deputy military commander," Guterres told reporters, referring to Swiss diplomat Christine Schraner Burgener.

Burgener was also in contact with other countries in the region, he said, adding: "We will do everything we can to make the international community united in making sure that conditions are created for this coup to be reversed."

De facto leader Aung San Suu Kyi was detained Monday and ousted from power, returning the country to military rule after a 10-year dalliance with democracy.

Guterres has branded the putsch "absolutely unacceptable."

But the UN Security Council has so far taken a softer line, voicing "deep concern" -- a step down from a draft Tuesday that had also condemned the putsch.

Diplomats said veto-wielding China and Russia, Myanmar's main supporters at the UN, had asked for more time Tuesday to finesse the council's response.