PANAMA CITY — A group of pro-government Cubans muscled their way into a closed-door meeting of grassroots activists Thursday, disrupting for the second day in a row a tension-filled meeting ahead of this week's Summit of the Americas.

The activists from across Latin America and the Caribbean were putting together proposals to present to U.S. President Barack Obama, Cuba's Raul Castro and some 30 other leaders at the summit starting Friday on topics ranging from protection of the environment to support for democracy in the region.

But repeating the frenzied scene of a day earlier, a boisterous group of some 40 Castro supporters stormed a hotel conference room to protest what they said was the exclusion of government-backed groups from Cuba and the presence of Cuban dissidents they called "mercenaries" and "terrorists."

Ramon Gelabert, a representative of an anti-poverty group from Chile, said he was disappointed by the Cubans' action, saying they unnecessarily distracted attention from the communist run-island's social achievements.

"It was two hours of shouting; things almost came to blows," said Gelabert.

The committee on civic participation, one of a half dozen working groups drafting recommendations for the leaders, later reassembled peacefully.

The U.S. State Department condemned what it said was "harassment" and "use of violence" against participants.

"It wasn't a good use of the civil society space provided by the summit," said Joy Olson, executive director of the Washington Office on Latin America, who had to elbow her way into the event. "But then the concept of civil society and its relation to the state is new for Cuba. I think that this is all part of the process of change."

The heckling and a street scrum Wednesday between supporters and opponents of Castro underscore the tensions surrounding Cuba's first-ever presence at the two-decade-old regional gathering.

Also stirring emotions, especially among the region's many leftist governments, are recent U.S. sanctions on seven Venezuelan officials for human rights abuses stemming from anti-government protests last year.

On Thursday, Obama said during a stop in Jamaica that he hoped to soon act on a State Department recommendation to remove Cuba from the U.S. government's list of state sponsors of terrorism, a move that would accelerate his efforts to restore full diplomatic relations between the two former Cold War enemies.

Host Panama is trying to keep politics at the margin of the summit, whose main theme is prosperity with equality.

But pro-government groups from Cuba and Venezuela say they are more representative of the aspirations of their populations than many of the opposition groups present.

Separately, a group of 25 mostly conservative former Spanish and Latin American presidents issued a statement in Panama calling for the immediate release of Venezuelan opposition leaders it considers political prisoners and which the government accuses of trying to violently oust President Nicolas Maduro barely two years into his term. They are also seeking guarantees that legislative elections expected later this year are fair and free.

"In some distinct situations silence isn't an option, it's tantamount to complicity," said former Spanish Prime Minister Jose Maria Aznar. They were accompanied by the wives of Venezuela's two-most prominent jailed opposition leaders, Leopoldo Lopez and deposed Caracas Mayor Antonio Ledezma.