AFP - An end to the US economic embargo on Cuba is still "way down the road," despite an unprecedented softening of rhetoric between the two countries, President Barack Obama's top economic advisor said.

"That's way down the road, and it's going to depend on what Cuba did, Cuba does going forward," advisor Larry Summers said in an interview aired Sunday on NBC television's Meet the Press program.

Summers said any substantial changes to the US-Cuba economic relationship would be "decided on the basis of Cuba's behavior, on the basis of the steps that they that they choose to take," and those "they choose not to take, in terms of their policies in this hemisphere."

His comments came after days of a remarkable change in tone between the Cold War foes.

On Friday, Obama seized on an extraordinary overture from Cuba to propose talks aimed at breaking the half-century of hostility.

"Let me be clear: I am not interested in talking for the sake of talking. But I do believe that we can move US-Cuban relations in a new direction," Obama said at a Summit of the Americas in Trinidad and Tobago.

"I am prepared to have my administration engage with the Cuban government on a wide range of issues -- from drugs, to migration and economic issues, to human rights, free speech and democratic reform."

On Thursday Cuban leader Raul Castro said "we are open, whenever they want, to discussing everything: human rights, freedom of the press, political prisoners -- everything they want to discuss."

But on Saturday, the White House tempered talk of rapproachement and called for action from Havana.

"Actions are always going to speak louder than words, regardless of how long the speeches are," White House spokesman Robert Gibbs told reporters.

"We will continue to evaluate and watch what happens, we are anxious to see what the Cuban government is willing to step up to do, and I think the president believes that significant action's been taken," said Gibbs.

A senior White House official, meanwhile, acknowledged that many Latin American leaders who met with Obama on Saturday at the summit had urged that he lift the US embargo on Cuba.

Obama said he understood how important the issue was for them, but reminded them that as democratically elected leaders they should also be concerned with democracy in Cuba, said the official who requested anonymity.

A US economic embargo on Cuba has been in place since 1962. Obama last week ordered an easing of the measures, lifting restrictions on travel and financial remittances to the island nation by Cuban-Americans.

Summers said any Obama decisions on Cuba "are really going to be grounded in what's best for the United States."