Myanmar’s de facto leader Aung San Suu Kyi has “a last chance” to halt an army offensive that has forced hundreds of thousands of the mainly Muslim Rohingya to flee abroad, the UN head has said.
Antonio Guterres told the BBC that unless she acted now, “the tragedy will be absolutely horrible”.
The UN has warned the offensive could amount to ethnic cleansing.
Myanmar says it is responding to last month’s deadly attacks by militants and denies it is targeting civilians.
The military launched its operation after the attacks on police in the northern Rakhine state.
In an interview with BBC’s HARDtalk programme ahead of this week’s UN General Assembly, Mr Guterres said Aung San Suu Kyi had a last chance to stop the offensive during her address to the nation on Tuesday.
“If she does not reverse the situation now, then I think the tragedy will be absolutely horrible, and unfortunately then I don’t see how this can be reversed in the future.”
The secretary-general reiterated that the Rohingya should be allowed to return home.
He also said it was clear that Myanmar’s military “still have the upper hand” in the country, putting pressure “to do what is being done on the ground” in Rakhine.
Aung San Suu Kyi – a Nobel Peace Prize laureate who spent many years under house arrest in the junta-run Myanmar (Burma) – is now facing growing criticism over the Rohingya issue.
She will not be attending the UN General Assembly in New York, and has claimed that the crisis is being distorted by a “huge iceberg of misinformation”.
She said tensions were being fanned by fake news promoting the interests of terrorists.
Mr Guterres’ warning comes after Bangladesh said it was now limiting the movement of more than 400,000 Rohingya who have fled from Myanmar.
Bangladeshi police said Rohingya would not be allowed to travel anywhere outside of their allocated homes, not even to live with family or friends.
Transport operators and drivers have also been urged not to carry refugees, with landlords told not to rent out any property to them.
Bangladesh also announced plans to build shelters for up to 400,000 people near the city of Cox’s Bazar.