Colombia expelled leading Venezuelan opposition figure Juan Guaido on Monday, hours after he arrived in Bogota for a conference on his crisis-torn country.
Neither Mr. Guaido, recognised in 2019 by more than 50 countries as Venezuela's de facto leader, nor Venezuelan President Nicolas Maduro were invited to attend the event.
The conference, organised by Colombia's President Gustavo Petro, seeks to restart negotiations between Venezuela's government and the opposition that began in Mexico City in 2021 but reached a deadlock in November.
Venezuela's opposition, backed by many countries including the United States, did not recognise Maduro's 2018 re-election in a vote widely dismissed as fraudulent.
The next year, Washington ramped up sanctions against Caracas, which were first imposed in 2015 over the brutal repression of anti-government protests.
Last month, a Venezuelan official said free presidential elections in 2024 were dependent on the lifting of sanctions.
Colombia's foreign ministry said Mr. Guaido, who arrived in Bogota in an "irregular manner", was taken to the capital city's El Dorado airport for a "departure on a commercial airline to the United States during the night."
"The ticket had already been purchased by him," the statement added.
Under Petro's predecessor, right-wing president Ivan Duque, Colombia had been Mr. Guaido's main regional backer, breaking diplomatic ties with Maduro's government.
The left-wing Petro reversed this decision, taking up instead a leading role in a process aimed at ending Venezuela's crisis through negotiations.
Mr. Guaido said in a statement he had walked across the border from Venezuela to Colombia.
"I have just arrived in Colombia, in the same way as millions of Venezuelans before me -- on foot," he said.
"I hope the summit can guarantee that the Maduro regime will return to the negotiation table in Mexico and that a credible timeline can be agreed upon for free and fair elections to be held as a solution for the conflict."
Mr. Guaido later posted a video on Twitter that he appeared to have filmed from inside a plane.
"After 60 hours on the road to get to Bogota, escaping the persecution of the dictatorship, defying the Maduro regime, they are taking me out of Colombia," he said.
Even though he was not officially invited to attend the conference, Mr. Guaido had hoped to hold talks with visiting officials on the sidelines of the meeting.
The conference is set to bring together nearly two dozen delegations from countries in Latin America, North America and Europe in an attempt to unfreeze negotiations between the government and opposition.
Mr. Guaido has also called for a protest to be held on Bogota's Plaza de Bolivar square, a short walk from the palace where the conference will take place.
Mr. Guaido, who led a symbolic "interim government" from 2019 until January this year, has rejected calls by Colombia's Petro for sanctions against Venezuela to be lifted.
Venezuela's divided opposition voted to disband its symbolic "interim government" in January and replaced Mr. Guaido as the head of a parallel congress made up of opposition lawmakers.