US President Barack Obama and Cuban President Raul Castro arrived in Panama for the Friday start of the Summit of the Americas, where the two are set to meet officially for the first time since declaring a thaw in bilateral relations that had been frozen for more than 50 years.

The two-day summit brings together leaders and delegates of 35 countries in the Americas, but all eyes were on the two former archenemies on the cusp of historic change.

The White House said before the summit that while no formal bilateral meeting was yet scheduled between Obama and Castro, they were expected to “interact” at the summit, at official meetings and on the sidelines.

“There are many opportunities for leaders to have conversations,” White House adviser Ben Rhodes said in a media briefing.

The meetings on Friday and on Saturday mark the first time Cuba has been invited to participate in the meeting of American democracies, and already on Thursday, change was in the air.

In Jamaica for a meeting of CARICOM before the summit, Obama said the State Department had finished reviewing Cuba’s request to be removed from the list of state sponsors of terror, a key demand in ongoing negotiations to reopen diplomatic relations.

A US senator, Ben Cardin, leaked the substance of the State Department’s conclusion, saying it had recommended removal from the list to Obama.

The State Department did not issue confirmation of the decision, but posted a picture on its official Twitter account of US Secretary of State John Kerry shaking hands with Cuban Foreign Minister Bruno Rodriguez in Panama late Thursday. The meeting was the first between the countries’ foreign ministers since they broke off diplomatic relations in 1961.

Cuba’s foreign trade minister Rodrigo Malmierca addressed a meeting of business leaders from 35 countries of the Americas Thursday, and invited them to look for business opportunities in Cuba, Panama’s national news agency reported. Malmierca said Cuba needs $2.5bn in foreign investment.

On Wednesday, pro-government activists brawled with dissidents protesting outside Cuba’s embassy in Panama City. Pro-Castro groups walked out of a civil society summit, refusing to share a forum with dissidents they called “mercenaries and terrorists.”

Panamanian President Juan Carlos Varela, the summit’s host, called for “respect”. He characterised the sparks as a “confrontation between Cuban brothers”, with “deep political differences and wounds that are healing”.

Tensions surrounding Venezuela threatened further fireworks at the summit.

For weeks, Venezuelan President Nicolas Maduro has demanded that Obama repeal heightened sanctions he imposed 9 March on seven Venezuelan officials accused of human rights abuses against political opponents. The US executive order called Venezuela a “threat” to US security.

The US has since backpedalled on the language, and a US envoy, Thomas Shannon, met on Wednesday in Caracas with Venezuelan Foreign Minister Delcy Rodriguez. There were also unconfirmed reports Shannon may have met Maduro, to discuss a potential meeting between Maduro and Obama in Panama City.

In Panama, the wife of imprisoned Venezuelan opposition leader Leopoldo Lopez, Lilian Tintori, attended a press conference Thursday where 25 former Latin American presidents and former Spanish president Jose Maria Aznar demanded the release of Venezuelan political prisoners.

The former leaders presented their “Panama Declaration” to the Organisation of American States.

Former Ecuadorian president Osvaldo Hurtado lamented the absence of Venezuela’s political crisis from the summit agenda, according to La Prensa newspaper.

Protests were heard on the streets of Panama as well. A group of Venezuelans marched against Maduro’s government, as did Nicaraguans against the planned construction of a new interoceanic canal. And indigenous groups from across the Americas demonstrated for recognition of their rights and against climate change. News24