A UN Security Council emergency meeting on the protests in Iran showed Tehran "the world will be watching" its actions, the US ambassador has said.
The US called the meeting after giving moral support to the anti-government protesters in a week of demonstrations and counter-demonstrations.
US president Donald Trump and members of his administration have praised the anti-government demonstrators as people standing up to a repressive and corrupt regime that is trying to silence them.
But Russia and some other countries said the UN's most powerful body had no business weighing in on the demonstrations.
"The world should applaud their courage" and amplify their message, said Ambassador Nikki Haley, portraying the protests as a human rights issue that could spill over into an international problem.
"The Iranian regime is now on notice: The world will be watching what you do."
But Russia and Iran complained the US was dragging a council focused on international security into what they called a domestic matter.
"The United States is abusing the platform of the Security Council," said Russian Ambassador Vassily Nebenzia, whose country has close ties to Iran, adding: "Let Iran deal with its own problems."
Envoys from several other countries, from China to newcomer Equatorial Guinea, expressed reservations about whether the council was the right forum for the issue.
The UN charter empowers to the council to "investigate any dispute, or any situation which might lead to international friction," and the US was not alone in thinking the Iranian protests qualified.
"It is right and proper - indeed, our responsibility ... to assess whether a situation like this could become a threat to international peace and security," British Ambassador Matthew Rycroft said before the meeting.
Dutch Ambassador Karel van Oosterom said his country hoped the meeting could "work as a preventive measure to avoid further escalation of violence".
He called on the Iranian government to set up a process to address any serious human rights violations and hold accountable anyone involved.
At least 21 people have been killed and hundreds arrested amid the anti-government protests and unrest over the country's economic woes.
Up to 42,000 people took part in the protests, according to Interior Minister Abdolreza Rahmani Fazli, who has said the clerically overseen government exhibited "tolerance" toward the demonstrations.
Meanwhile, tens of thousands of people have attended pro-government rallies in recent days. Authorities say the anti-government protests are waning.
French Ambassador Francois Delattre urged the council to react carefully, "with all the vigilance required ... but guarding against any exploitation of this crisis, which would only reinforce the extremes."
Iran's prosecutor general, Mohammad Jafar Montazeri, alleged on Thursday that an American CIA official was the "main designer" of the demonstrations.
Iranian Ambassador Gholamali Khoshroo - whose country isn't a Security Council member but was invited to participate on Friday - said the protests had received "direct encouragement by foreign forces including by the president of the United States."
The Trump administration has denied having any hand in the demonstrations, saying they arose completely spontaneously. The CIA declined to comment.