US-backed opposition leader Juan Guaido, who more than 50 countries recognize as interim president, had been leading a push to oust leftist firebrand Maduro, who presides over a crumbling economy.
But the opposition agreed to come to the table under Norwegian auspices after an army uprising coupled with street protests, which Guaido hoped would deal decisive blow, instead fizzled out a month ago.
Norwegian diplomats had said that the two sides would meet this week in Norway in their first face-to-face meeting since Guaido claimed power in January, without specifying a date or venue.
Sources close to the process told AFP that the talks were taking place in Oslo. The Norwegian foreign ministry declined to comment.
Maduro, while describing the opposition as "extremist" and working on behalf of the United States, promised to make an effort to resolve the crisis.
"We are going to be showing our very best good faith... to be able to find, based on the platform the parties agreed on, peaceful, democratic solutions to help overcome Venezuela's conflict," Maduro said in a televised address Monday.
US firm in shunning Maduro
The United States has refused to speak to Maduro on anything but logistical matters, calling his leadership illegitimate. While not rejecting the talks in Oslo, the United States stood firm in its stance.
"We note the talks in Norway. As we have repeatedly stated, the United States believes the only thing to negotiate with Nicolas Maduro is the conditions of his departure," State Department spokeswoman Morgan Ortagus told reporters in Washington.
"While previous efforts to negotiate have failed because the regime has used them to divide the opposition and gain time, we hope that the talks in Oslo will focus on the departure of Maduro as a precondition for progress."
In a symbolic rejection of Maduro, whose government is still recognized by the United Nations, the United States walked out of the Conference on Disarmament in Geneva as Venezuela assumed the UN body's rotating presidency.
"Whatever is discussed in there, whatever is decided, has absolutely no legitimacy because it is an illegitimate regime presiding over that body," the US ambassador to the conference, Robert Wood, told reporters outside the council's chamber.
President Donald Trump, who has cast Venezuela as part of a broader struggle against socialism, has tried to topple Maduro by imposing an escalating raft of economic sanctions that have included cutting off revenue for Venezuela's state-owned oil company.
Millions of Venezuelans have fled the country as astronomical inflation and broader economic woes have made food and basic supplies unobtainable for average people.
Maduro, however, still enjoys the support of Russia, China and Cuba, as well as his own country's powerful military.
Opposition still seeks pressure
ALnavio, a Madrid-based newspaper that covers Latin American affairs, said the main issue in Oslo was the question of staging "free and fair" elections as demanded by Guaido, who leads the elected National Assembly shunned by Maduro.
The opposition leader defended the decision to send representatives to Oslo as he addressed supporters Sunday in Venezuela's Lara state, saying that "we have to play on all the boards."
But he said his demands had not changed.
"Whoever wants us to renounce the pressure in the street or in international scenarios in order to stop the takeover, becomes an accomplice of the dictatorship," he tweeted.
Maduro's delegation includes Communication Minister Jorge Rodriguez, Miranda state Governor Hector Rodriguez and Foreign Minister Jorge Arreaza.
Representatives of the two sides met separately with their Norwegian hosts earlier this month.
Reports said the mediation effort was being led by Dag Nylander, who played a key role in the 2016 peace accord between the Colombian government and FARC rebels.