UN Secretary General António Guterres has urged the world community to make sure Monday's coup in Myanmar fails.
The reversal of elections is "unacceptable", he said, and coup leaders must be made to understand this is no way to rule the country, reports BBC.
The UN Security Council is discussing a possible statement, but China is expected to block any form of words which condemns the coup.
Elected leader Aung San Suu Kyi was detained when the army seized power.
Police in Myanmar - also known as Burma - later filed several charges against Ms Suu Kyi, who has been remanded in custody until 15 February.
Neither Ms Suu Kyi nor deposed President Win Myint have been heard from since the takeover.
The coup, led by armed forces chief Min Aung Hlaing, has seen the installation of an 11-member junta.
The military, which has declared a year-long state of emergency, sought to justify its action by alleging fraud in last November's elections, which Ms Suu Kyi's National League for Democracy (NLD) won decisively.
Facebook services in Myanmar were disrupted on Thursday amid reports the military had ordered telecom companies to block the social media platform.
The company confirmed the disruptions, urging "authorities to restore connectivity so that people in Myanmar can communicate with their families and friends and access important information".
Over the past days, activists had set up Facebook pages to co-ordinate opposition to the coup.
The UN secretary general called for constitutional order to be re-established in Myanmar. He said he hoped there would be unity in the Security Council on the matter.
"We'll do everything we can to mobilise all the key actors of the international community to put enough pressure on Myanmar to make sure that this coup fails," he said.
"It's absolutely unacceptable to reverse the result of the elections and the will of the people.
"I hope that it'll be possible to make the military in Myanmar understand that this is not the way to rule the country and this is not the way to move forward."
Western countries have condemned the coup unreservedly, but efforts at the Security Council to reach a common position failed as China dissented. China is one of five permanent members with a right of veto in the council.
Beijing has long played a role of protecting the country from international scrutiny, and has warned since the coup that sanctions or international pressure will only make things worse.
Alongside Russia, it has repeatedly protected Myanmar from criticism at the UN over the military crackdown on the Muslim minority Rohingya population.