CARACAS, VENEZUELA—South American nations suspended Venezuela on Friday from the Mercosur trade group over what they said was its failure to comply with the commitments made when it joined the group in 2012.

Argentina’s foreign ministry said in a statement that Venezuela had failed to meet a Thursday deadline to adopt certain standards required for membership. The foreign ministers of the four founding members — Argentina, Brazil, Uruguay and Paraguay — notified Venezuela’s government of the decision in a letter.

Mercosur accepted Venezuela as a member when South America was dominated by leftist governments in an effort to link the region’s biggest agricultural and energy markets.

But the socialist-run Venezuela fell afoul of its neighbours as it cracked down on the opposition and conservative governments assumed power in Argentina and Brazil. Venezuela’s regional influence also waned as the country cut back on oil shipments once provided to allies at cut-rate prices.

This strong rebuke from Venezuela’s one-time friends could open the door to stronger action from countries and regional blocs. The head of the Organization of American States for months has threatened moves against Venezuela for its increasing authoritarianism. Some U.S. Congress members have called for sanctions and other forms of pressure.

Venezuela’s Foreign Minister Delcy Rodriguez said Friday she had not been informed of the suspension. She rejected the notion that Venezuela had failed to conform to the trade group’s rules.

“Venezuela does not recognize the null action carried out under the law of the jungle taken by the officials who are destroying Mercosur,” she said.

Earlier in the week, Venezuela’s opposition coalition threatened to walk away from ongoing dialogue with the socialist government. The Vatican-mediated talks were intended to head off a growing political crisis as critics of President Nicolas Maduro allege he has become a dictator and call for him to resign.

Venezuela has arrested hundreds of opposition activists in recent years and stifled opposition media. A local human rights group counts 100 political prisoners still in jail. This fall, the government killed an effort stage a recall referendum against Maduro.