The expulsion of a top Venezuelan opposition leader from a summit meeting on pluralism can be seen as a kind of flare — one signaling that American foreign policy is failing in the heart of South America. 

President Petro of Colombia expelled a top Venezuelan opposition leader Tuesday from a Bogota summit, endorsed by President Biden, that purports to bring pluralism to the Marxist dictatorship of Venezuela.

Until recently, the expelled opposition leader, Juan Guiado, the National Assembly speaker, was recognized by Washington as the legitimate leader of Venezuela. He and his family now face threats by the regime of President Maduro. His Tuesday expulsion from Bogota was aided by a tip from Washington, according to Colombia’s foreign minister, Alvaro Levya. 

The Colombian government expelled Mr. Guaido shortly after he arrived at Bogota to participate in the summit, which is being attended by representatives of the region’s leftist governments as well as top Washington officials.

There is a dispute as to whether Mr. Guiado was invited to the gathering in the first place. Nevertheless, he traveled to Colombia on Monday night to participate in Mr. Petro’s global meeting that aims to resume negotiations between Mr. Maduro and the Venezuelan opposition. 

“The dictatorship’s persecution extended to Colombia, unfortunately,” Mr. Guaido said in a video, shot while he was boarding a flight to Miami. Mr. Leyva invited the opposition to the meeting, Mr. Guaido said, adding, “I specifically came to bring the voice of millions of Venezuelans that want a better country.”

Colombia’s foreign ministry denies that it invited either Mr. Maduro or the opposition to the summit. Delegations from 20 countries will meet Tuesday to promote dialogue between Mr. Maduro and the opposition and to set a date for fair and free Venezuelan elections.

The summit’s main goal, though, may extend beyond the promotion of democracy in Caracas. During a meeting with President Biden last week, Mr. Petro said he hoped it would push Washington to begin lifting sanctions against Venezuela.

Over the weekend the White House listed the high-level officials that will travel to Colombia for the summit, including a deputy national security advisor, Jon Finer; the special presidential advisor for the Americas, Chris Dodd; and the National Security Council senior director for the Western Hemisphere, Juan Gonzalez. 

In a gesture to the Venezuelan dictator, Washington in January rescinded its recognition of Mr. Guiado as Venezuela’s interim president. President Trump recognized Mr. Guiado as the legitimate president of Venezuela in 2019.

In a statement issued on Monday Mr. Guaido said he arrived in Bogota after driving across the border between the two countries. He was there to meet with the Venezuelan diaspora. “I hope the summit can guarantee that the Maduro regime returns to the negotiating table,” Mr. Guaido said. 

Mr. Guaido said Mr. Maduro is attempting to intimidate him and his family in an effort to silence the opposition. “I am not going to allow that,” Mr. Guaido said, adding that despite knowing the risks of leaving Venezuela and seeking support from world leaders, he will move forward with his plan.

Yet, later that night, Colombia’s chancellery announced that Mr. Guaido, “who was in Bogota illegally,” was escorted out of the country by Colombian migration officials that verified “his departure on a commercial airline to the US, during the night.”

On Tuesday morning, Mr. Levya told the press that an American official told them where Mr. Guaido was staying at Bogota. He also confirmed that the American government provided the flight ticket to Miami, Florida, where Mr. Guaido arrived Tuesday morning.

“The doors have not been closed to anyone,” Mr. Levya said. “This is not a country that expels, it is a country that seeks to comply with the constitution and the law.” America’s collaboration with Colombia’s government, Mr. Levya said, shows Washington’s “interest that today’s meeting is fully successful.”

Treating Mr. Guaido “as an inconvenience” for Mr. Petro’s Venezuelan meeting “misses the point entirely,” the director of the Americas Program at the Center for Strategic and International Studies, Ryan Berg, says. “Guaido’s presence in Colombia is to escape a sense of imminent arrest” by the Venezuelan dictator, he says.

Mr. Maduro, who met Mr. Levya in Caracas last week, fully supports the Bogota summit. There are “great expectations” for the conference, Mr. Maduro said on his new state-run television show. The “international community has only one voice” and is united behind the idea of “zero sanctions against Venezuela,” he said.