Nicaragua on Friday began the process of leaving a Washington-based regional cooperation body that rejected President Daniel Ortega's reelection two weeks ago.
Exiting the Organization of American States (OAS) will take about two years as Nicaragua fulfils its obligations.
The Central American country's congress on Tuesday asked former Marxist guerrilla Ortega to withdraw from the OAS, which had stated the November 7 election "was not free, just or transparent and had no democratic legitimacy."
"I am writing to you to officially announce our unwavering decision to denounce the OAS charter ... that initiates the definitive withdrawal and resignation of Nicaragua from this organization," Foreign Minister Denis Moncada wrote in his letter to OAS General Secretary Luis Almagro.
Ortega, 76, was reelected to a fourth consecutive term with 75 percent of the vote but the result was largely rejected by the international community, including the United States and European Union.
In the months leading up to the election, Nicaraguan authorities detained almost 40 opposition figures, including seven potential presidential candidates, while also disqualifying the main opposition alliance from taking part.
The measures left Ortega with no genuine opposition.
Ortega ruled Nicaragua from 1979 to 1990, after the guerrilla ousting of US-backed dictator Anastasio Somoza.
Since returning to power in 2007, he has become increasingly authoritarian and quashed presidential term limits.