PANAMA CITY — Nicolas Maduro had barely gotten off his plane at the Summit of the Americas on Friday before he gave a symbolic poke in the eye to Washington, paying a visit to a monument honoring victims of the 1989 U.S. invasion of Panama.

A crowd of several hundred, many of them government supporters flown in from Venezuela, greeted the socialist leader at the memorial in the poor downtown neighborhood of El Chorrillo, which saw the heaviest fighting during the invasion. "Maduro, stick it to the Yankee!" they chanted.

Maduro said he would personally deliver to President Barack Obama the victims' petition demanding the U.S. apologize for the military incursion that removed dictator Gen. Manuel Noriega and compensate families who lost loved ones.

"Never again a U.S. invasion in Latin America," Maduro said.

The Venezuelan leader has hardened his rhetoric against Washington in the run-up to the summit after the White House slapped financial sanctions on seven senior officials it accuses of human rights abuses tied to last year's anti-government protests.

At the rally, organizers canvassed locals to add their name to a petition that Maduro has promised to deliver to Obama with 10 million signatures calling on the U.S. president to reverse course.

Shirtless children waiting around for hours in the scorching midday heat posed for photos holdings signs stamped with what has become a ubiquitous rallying cry in Caracas: "Obama Repeal the Executive Order."

Despite Maduro's aggressive rhetoric all eyes are on Obama and Cuba's Raul Castro at the summit, where the two leaders are expected to meet for the first time since their historic December announcement that they would move to restore diplomatic relations severed since 1961.

Other Latin leaders were also going about their business: meeting on the sidelines among themselves and with educators, corporate CEOs and civil society groups.

Enrique Pena Nieto of Mexico got together with Juan Manuel Santos of Colombia and Ollanta Humala of Peru, bringing together the presidents of the South American nations that are the two biggest sources of coca leaf, the raw ingredient in cocaine, and the leader of the United States' immediate southern neighbor, a major transit corridor for the drug.

The presidents of Central America's "northern triangle" — Guatemala, El Salvador and Honduras — asked the United Nations for support for a security and development plan that also aims to reduce emigration from the violence-plagued countries toward the United States.

The three presidents delivered to U.N. Secretary-General Ban Ki-moon a document outlining their strategy and met with Obama, who has requested $1 billion in aid for Central America in his budget proposal to Congress.

Guatemalan President Otto Perez Molina and Honduran President Juan Orlando signed an agreement to launch a border customs union that aims to ease the flow of people and goods between the two countries, something they have long aspired to create.

"We are taking important steps in the processes of integration and attracting investment with this customs union," Perez Molina said.

Bolivian President Evo Morales made time for a friendly soccer match Friday with delegates to the alternative Peoples' Summit. Known for regularly kicking the ball around with different groups as part of his presidential outreach, Morales donned a white-and-green No. 10 jersey with "Evo" on the back.

A separate civil society forum was the scene of a third day of confrontations between opponents and supporters of the Cuban government, prompting police to get between the two camps and close off access to the venue for nearly 40 minutes.

Castro supporters shouted "Mercenaries!" as they faced off with government opponents who brandished signs such as "Democracy is respect."

The pro-Castro delegation later walked out of the forum before Obama's scheduled closing speech, complaining that they had been "forced" to share the stage with opposition figures they consider hostile to their country..

"With respect to the host president and the other leaders, including President Obama, the delegation of the authentic Cuban civil society has decided not to take part in the encounter," they said in a declaration read by member Rosa Maria Perez.

At the Panama invasion monument, Trinidad Ayola, who lost her husband in the fighting, held back tears as she talked about Maduro's visit. She said it was the first time any Panamanian leader or foreign head of state had come calling in the two decades since the monument was built, and she called on Obama to apologize for the 1989 invasion.

"Maduro is interested in the suffering of the people," she said, contrasting the Venezuelan's visit with Obama's to the American-built canal. "All Obama cares about is the interests of the multinationals."