Supporters of the government of Venezuelan President Nicolás Maduro protest new U.S. sanctions in Caracas on Wednesday. Their signs read, “Trump unblock Venezuela.” (Leonardo Fernandez/AP)

The decision of President Nicolás Maduro to pull out of talks with Venezuela’s opposition cast a new shadow over hopes for a peaceful resolution to the political stalemate that has paralyzed the crisis-wracked South American nation.

The sides had planned to sit down Thursday for a sixth round of negotiations mediated by Norway, but Maduro said he wouldn’t send a delegation to the talks in Barbados after President Trump ordered stiff new sanctions against his government.

“The people have asked me why I’m in a dialogue with people who have tried to assassinate, overthrow and fill the country with violence, but we have still done it,” Maduro said in a televised phone interview late Wednesday. “In this case, we cannot sit down with people who celebrate this criminal economic blockade that the U.S. has imposed on us.”

He called instead for a march on Saturday to reject the embargo.

The opposition delegation, sent by National Assembly President Juan Guaidó, was already on the Caribbean island.

“We are in Barbados to seek an agreement that ends Venezuelans’ suffering,” Stalin González, who has represented the opposition in the talks, wrote in a tweet.

He said Maduro’s government had “spent days saying that they believe in peace and the Oslo mechanism, but they fear the possibility of a real political change in the country.”

Trump administration officials have been skeptical of the negotiations. National security adviser John Bolton dismissed them this week as “not serious.”

Venezuelan government officials did not say whether or when they might be willing to resume discussions.

Guaidó said Thursday that his opposition team had sat in negotiations with “skepticism and lack of trust” in the first place and that the government was an “obstacle” to reaching a solution. But he predicted the talks would continue.

“Yesterday, the regime announced last minute that it wouldn’t participate in the new round of conversations,” the opposition leader said in a videotaped statement posted on social media. “Sooner rather than later they will sit back down.”

Analysts said the pullout adds more uncertainty to the stalemate.

“The negotiation doesn’t die, but it’s prolonged, it gets stuck,” said Luis Vicente León, director of the Caracas polling agency Datanalisis. “It’s not surprising that after the extreme sanctions, the government’s response is to radicalize its position, and it is likely that we will soon see actions against opposition leaders.”

Félix Seijas, director of the Delphos polling agency, called Maduro’s move “propaganda.”

“The government is sending a message of strength to its people and using the opportunity to blame the U.S. for generating chaos,” he said. “It means the resolution is even less likely to come soon, but it doesn’t mean the talks are over.”

Seijas said delays can cost the opposition support.

“People get disillusioned,” he said. “They either get mad at Guaidó or lose hope that the opposition’s actions will bring change.”

President Trump announced the embargo on Monday after months of escalating sanctions on government officials and institutions in this collapsing oil nation, devastated by more than a decade of economic mismanagement. More than 4 million people have fled amid hyperinflation, power outages and shortages of food, water and medicine.

The new sanctions freeze government assets and prohibit transactions with its officials, putting the country on similar footing with Cuba, Iran, North Korea and Syria.

The Venezuelan government has described the embargo as an attack against the whole population.

“President Nicolás Maduro Moros has decided not to send the Venezuelan delegation this time given the brutal and grave aggression perpetrated by the Trump administration against Venezuela,” the Foreign Ministry said in a statement Wednesday evening.

Guaidó, recognized by the United States and more than 50 other nations as Venezuela’s rightful leader, has defended the embargo, arguing that it will protect the country’s assets and prevent the government from benefiting from business with foreign investors. He has noted that it includes “humanitarian exceptions” for food and medicines and says it will protect the private sector.

Maduro claimed victory last year in elections widely viewed as fraudulent. His government is accused of jailing, torturing and killing adversaries.

The opposition-led National Assembly declared Guaidó interim president in January.

Guaidó has called for free and fair elections. But after quickly rallying support from a majority of Venezuelans early this year, he has struggled to maintain momentum. Polls show that the number of Venezuelans who say they think change will come in the short term has dropped in recent months.

The government and the opposition sat down for a first round of talks in May.

Mariano de Alba, a Venezuelan lawyer based in Washington, said the embargo is a sign that the administration is unhappy with the negotiations. Administration officials, he said, believe “pressure has to increase, specifically economic pressure.”

But that pressure could also bring the government back to the table. The opposition skipped a planned round of talks last month after the death in government custody of dissident military officer Rafael Acosta Arévalo. Discussions resumed a week later.

On this occasion, opposition leaders have insisted on their willingness to continue negotiations. Polls show that half of the country’s population, and a majority of Guaidó’s supporters, back the talks.

Guaidó said Thursday that if negotiations don’t work, the opposition would “achieve change through other mechanisms because the path is irreversible. This dictatorship will fall, the question is when.”

Analysts and ordinary Venezuelans have expressed concern that U.S. sanctions could hit the population hard without accelerating Maduro’s exit. The president still controls the military.

Maduro called out Bolton in his televised phone interview.

“John Bolton, with all his hate, won’t be able to fight us,” he said. “Bolton should be worried about indiscriminate violence in his own country.”