Representatives from Venezuela’s government and the opposition alliance agreed to tone down fierce rhetoric and hold further meetings amid a political standoff after a first round of exploratory talks about a Vatican-mediated dialogue.

“The government and opposition promised to diminish the aggressive tone of the language being used in the political debate,” Claudio Maria Celli, the Vatican’s representative, read in a statement after the talks concluded early Monday, adding that the meeting was “constructive and respectful.”

The opposition and government agreed to set up four working groups to discuss issues including the respect for the rule of law and national sovereignty; human rights and reparations to victims; the economy; and the generation of confidence and the electoral schedule, Celli said, adding that the current situation of political prisoners in the country would be reviewed. The opposition alliance, known as MUD, said in a separate statement that the next formal meeting would take place Nov. 11.

As state television showed images of the meeting earlier Sunday evening, with President Nicolás Maduro seated at the head of a negotiating table, the opposition alliance said in a separate statement that it would walk away from any talks if its demands to end “repression and persecution” and free political prisoners weren’t met soon.

“We have to be optimistic when it comes to peace,” Maduro said earlier in the night during televised comments from the talks. “There is no alternative to dialogue.” State television didn’t immediately carry any comments from the opposition’s delegation.

Maduro met with Pope Francis in Rome last week after the opposition alliance confirmed that the Vatican had sent a representative to Venezuela’s capital. Tensions have been rising since the national electoral council earlier this month suspended a recall referendum process against Maduro being sought by the opposition.

Last week, Maduro threatened to jail anyone he accused of violating the constitution, including lawmakers, as the opposition-controlled National Assembly summoned him to testify in a political trial set for Tuesday. After a lukewarm turnout for a one-day national strike that opposition called Friday, Maduro made a sexual reference in front of assembled schoolchildren and said the opposition “needs a little Viagra to see if they can get something up in the country.”

The opposition alliance, which has called on supporters to march to the presidential palace Thursday if the referendum process wasn’t reactivated, said Sunday in its statement that it would maintain its protest agenda to push for urgent political change. While representatives of three opposition parties including Accion Democratica, Un Nuevo Tiempo and the Primero Justicia party led by Gov. Henrique Capriles attended the talks, the Voluntad Popular party, which is led by its jailed leader, Leopoldo Lopez, did not attend.

Voluntad Popular may join the talks at a later date if its conditions that include the release of political prisoners are addressed, MUD said.

Maduro’s administration is engaging in the Vatican-mediated talks to alleviate international pressure, divide the opposition and buy time, according to the Eurasia Group, a political risk consultancy.

“While the government may strike a more conciliatory posture in the coming weeks, talks are unlikely to resolve the political crisis as the government remains fundamentally unwilling to cede to opposition demands and release its grip on power,” Eurasia Group analysts Risa Grais-Targow and Agata Ciesielska wrote in a report Monday.

Thomas Shannon, the U.S. under secretary of state for political affairs, will travel to Caracas on Monday and stay until Wednesday.