Protests in Venezuela left at least 20 people dead and many more wounded this week, the United Nations' human rights office said Friday.
U.N. human rights chief Michelle Bachelet said in a statement she's "extremely concerned that the situation in Venezuela may rapidly spiral out of control with catastrophic consequences."
She called for both sides to have a dialogue soon.
Countries like China, Russia and Turkey support Maduro, who won an election in May that was boycotted by political opponents.
Guaido, leader of the country's National Assembly, will make a speech Friday morning, when he is expected to talk about his next steps as interim president.
In a radio interview Friday cited in The New York Times, Guaido urged Venezuelan diplomats in the United States to keep working and refuse orders to return home, an act of defiance as Maduro attempts to cut all U.S. ties.
Guaido also wants to bring humanitarian aid to Venezuela. He was talking from an undisclosed location.
U.S. diplomats still in Venezuela remain inside the embassy in Caracas after disobeying Maduro's order to leave the country by Saturday, The Washington Post reported. The act of defiance could lead the regime to cut electricity and gas service to the embassy. The State Department ordered many non-essential employees and their families to come back to the United States.
U.S. officials said there are no plans to completely close the embassy, adding that senior staff will stay.
Trump called Maduro an illegitimate leader.
"This is, at heart, a crisis of governance, and it is the responsibility of the country's leaders to put an end to this disastrous situation," said Bachelet, who served two terms as Chile's president. "What more is needed before the political leadership put their people's well-being ahead of their own interests?"