The meeting on a sunny Havana square was a little bit revolutionary for Cuba's revolution. And for U.S. diplomacy as well.
Dozens of young bloggers and tweeters gathered to talk about their place in a socialist society whose leaders have referred to the Internet as "a wild colt" to be tamed and make access difficult for all but a few.
Among them were some of the staunchest defenders of Fidel and Raul Castro's communist system. And there, too, stood what many consider their chief foe, in the guise of an affable, silver-haired stranger clad in sandals, khakis and a Hawaiian shirt.
Since arriving at the U.S. Interests Section in Havana nine months ago, Conrad Tribble has become perhaps its tweeter-in-chief, while reaching out to some of Washington's most vocal critics.
The Interests Section, which stands in for an embassy due to lack of full diplomatic relations, for years has cultivated ties to dissident bloggers and tweeters, who are widely scorned by Cuba's leaders and their cybernetic supporters as "mercenaries."
So the appearance of a U.S. diplomat at the May 10 meet-up of Cuba's pro-government Twitteratti has prompted alarm, wariness and a little bemusement.
"Imagine, the Interests Section meeting with revolutionary bloggers ... What the hell are we doing wrong?" asked a post by a sharp-tongued tweeter who uses the handle Yohandry Fontana.
Tribble mostly listened for about an hour as others talked about things like the challenges of getting online in a country with the lowest Internet connectivity rate in the Western Hemisphere.
A brief video of him speaking that circulated on Cuban blogs and was tweeted by the Interests Section's official account shows an encounter empty of the heated rhetoric that usually characterizes the Havana-Washington divide.
Tribble urged discussion on areas where the two sides agree, such as a love of baseball, and where they do not, such as the case of five Cuban agents who were given long prison terms in the U.S. He invited everyone to continue the conversation on Twitter.
Cuba "is a nation with many aspects that are unknown on the outside. ... I hope to have the chance to take part in a dialogue," he said in the clip.
Tribble, the No. 2 official at the U.S. mission, declined to be interviewed because he was not authorized to do so by the U.S. State Department. But he sends out up to a dozen blasts each day on everything from Cuba news to his beloved Bayern Munich soccer club.
His interactions with those who criticize the U.S. are often remarkably cordial.
When Elaine Diaz, a University of Havana professor and author of the Polemica Digital blog, complained about being denied a visa to attend the Latin American Studies Association conference in Washington in late May, Tribble tweeted that he'd look into it.
Two days later she was thanking the Interests Section for reversing itself and granting the visa. "I'm very happy for you!" Tribble wrote.
He also pushes back at what he considers over-the-top attacks.
When Yohandry Fontana joked that noted dissident blogger Yoani Sanchez would be unhappy with Cuba's new chief of parliament because he "wasn't proposed by Washington," Tribble shot back, "We didn't propose anyone."
And he added, "But we do notice that on the same day many Cuban dissidents are arrested. Democracy?"
In Cuba the Internet is one of the few avenues for a U.S. diplomat to get his message to more eyeballs — even if relatively few islanders have access to the Web. The state and Communist Party control nearly all media and rarely mention the U.S. envoys other than to accuse them of conspiring with Cuba's enemies.
And Washington is eager to reach a more diverse audience, as shown by a leaked U.S. diplomatic cable published in 2010 by WikiLeaks that described the small opposition as aging, ineffective, torn by infighting and hopelessly out of touch with most Cubans.
"I think it's a great idea," said Ted Henken, a sociologist at Baruch College in New York who is working on a book about social media in Cuba. "It's probably actually more important for the U.S. government and its diplomatic representatives to be in contact with people it doesn't agree with on most issues."
Tribble said in the video that he was inspired to take part by curiosity about how islanders use Twitter, but some ascribed more cynical motivations.
Journalist and blogger Iroel Sanchez, who was not at the gathering, called it a "provocation." Carlos Alberto Perez at a blog called La Chiringa de Cuba wrote that Interests Section officials are deluded if they think that through "lies, harassment and subversion of young people who coexist online, a sincere friendship or relationship of any kind will flourish."
But after Tribble emailed to reassure Perez of his good faith, Perez wrote a more softly worded response that ended with an invitation to keep up the debate online.
Cuba and some other Latin American nations have repeatedly alleged that the U.S. is waging a "cyber war" with Twitter and other media to gain influence around the globe. Havana points to the Arab Spring uprisings as examples, even as it insists nothing like that will work here.
Just 2.9 percent of islanders report having full access to the full World Wide Web, according to government statistics, though the true number is believed to be slightly higher. But official rhetoric, at least, has begun tilting toward a more open attitude.
"Today, with the development of information technologies, of social networks, of computing and the Internet, prohibiting something is almost a chimera, impossible," new Vice President Miguel Diaz-Canel said recently. "It makes no sense. ... We must constantly be in dialogue."
Alejandro Cruz, one of the organizers of the tweet-up, said he was surprised by Tribble's participation. But "it was an open, free space, and anyone who wanted to speak was allowed to. I think he just wanted to impart a message of soft power, something like: 'Guys, don't worry, we're not evil, even though it seems like it because we're been blockading you for more than 50 years.'"
Last Friday, former Cuban diplomat Carlos Alzugaray wrote a letter published on Cruz's blog saying that respectful dialogue with some American diplomats can be possible and even productive.
"Opening the doors to Mr. Tribble is an intelligent, courteous and appropriate step. The response cannot be silence. ... If Mr. Tribble wants to know how we Cubans think about all trends and opinions; receiving and listening to him strengthens, not weakens us," Alzugaray wrote.
"Although there are more than enough reasons to mistrust, nothing is lost by giving him the benefit of the doubt," he concluded.
Since the gathering, Tribble has picked up at least a dozen new Twitter followers who appear to be pro-Castro islanders. Some wrote to thank him for attending the session. One tweeted his delight at discovering their shared devotion to Bayern Munich.
Henken said tweeting to critics and meeting them in person can help civilize the tone of debate.
"It puts those people on the spot, so to speak, meaning that this guy is a human being standing there in the park with his sandals and a Hawaiian shirt on, and he's speaking in Spanish, and he's open to hearing their arguments," Henken said. "It kind of undermines the idea of the 'big-bad-wolf enemy who isn't interested in what we have to say.'"