Washington: US President Barack Obama will attend a Summit of the Americas in Panama this week, a gathering that could see the first substantive meeting between US and Cuban leaders in half a century.

Obama, fresh from reaching a tentative nuclear accord with Iran, will jet to Jamaica then on to Panama City on Thursday for a regular meeting of continental leaders.

Raul Castro — who took control of the 11-million-strong still nominally Communist island from his brother Fidel seven years ago — has confirmed he will be the first Cuban leader to attend.

But with days to go, diplomats are still discussing what form a Castro-Obama meeting might take.

Options range from a simple “grip-and-grin” photo, to a historic head-to-head sit down.

“The leaders are together a lot of the time,” at the summit said senior State Department official Roberta Jacobson. “And so there will be an interaction with Raul Castro.”

In December 2013, amid an upwelling of amity that followed Nelson Mandela’s death, the pair shook hands briefly at a memorial service in Johannesburg.

This time around, officials are looking for something a bit more substantive.

“It’s useful, obviously, to be able to have that contact and move things along so that we can get things done and open embassies and move ahead with this relationship,” said Jacobson.

Last December, Obama declared he would “end an outdated approach” to Cuba that was seeped in Cold War animosity and marked by crises that defined a generation — the Bay of Pigs, the 1962 Missile Crisis.

Obama said diplomatic relations would be restored and the US would move toward ending a crippling embargo that Cuba says has cost it more than one trillion dollars (Dh3.6 trillion) over five decades.

Since the pronouncement, both sides have taken baby steps toward ending the US policy of isolation.

Phone lines were reconnected, replacing crisis hotlines. Airbnb even launched listings for American visitors.

A recent poll of Cuban Americans by Bendixen and Amandi showed 51 per cent thought Obama’s policy of normalising ties was the way to go.

That could have deep repercussions for the fate of the embargo, which only the US Congress — long swayed by influential emigre groups — can end.

But Cuba-US relations remain fraught and a decision on a head-to-head presidential meeting may come down to the wire.

Cuban non-governmental groups critical of the regime, including Las Damas de Blanco, have been invited to attend a civil society meeting that will run parallel to the Panama leaders’ summit.

Obama is expected to address that gathering, although in an apparent concession, will hold a question-and-answer session in private, away from the press.

If the non-governmental groups are barred from leaving Cuba, or Obama looks like he will be harshly critical of the regime in his remarks, all bets may be off.

The Panama summit will also mark the first time in a generation that an American president meets continental leaders and is not harangued about US sanctions on Cuba.

Washington’s isolation policy has been deeply unpopular in Latin America, although US officials have frequently accused Cuba’s allies of hiding behind the dispute to avoid dealing with tough questions about their own countries.

But there is a risk that this time around it is US sanctions against Venezuela which may be the cause of Latin American unease.

With the stage set for a constructive meeting, Obama shocked Latin American allies by introducing sanctions against members of Nicolas Maduro’s regime.

Obama ordered the freezing of the US property and bank accounts of seven officials, including the former national guard chief Antonio Benavides, intelligence chief Gustavo Gonzales and national police chief Manuel Perez.

Venezuela’s leftist regional allies, many of whom receive critical economic aid from Caracas, jumped to Maduro’s defence.

The 11-nation “Bolivarian Alliance” including Raul Castro, Evo Morales of Bolivia and Daniel Ortega of Nicaragua gathered for a summit to condemn the move.

Organisers still hope the summit can end with a pledge to take concrete measures in areas where there is general agreement: security and the environment among them.