Former Cuban leader Fidel Castro, reacting to an Americas summit yesterday, urged US President Barack Obama to end a nearly half-a-century-old US economic "blockade" of Cuba.

"I would like to remind him of an elementary ethical principal that has to do with Cuba," Mr Castro wrote about President Obama on the website Cubadebate.

"Continued injustice or crime cannot be justified regardless of the era in which it has occurred," the Caribbean island nation's revolutionary leader continued.

"The cruel blockade against the Cuban people costs lives and results in human suffering."

Mr Castro also lamented what he described as "evasive and terse" remarks by the US President about Cuba on Sunday at the closing of the Summit of the Americas in Trinidad and Tobago.

Speaking in Port of Spain, Mr Obama admitted that the half-century US policy on Cuba "hasn't worked" because Cubans "aren't free". But he cautioned it would not be changed soon.

"The issues of political prisoners, freedom of speech and democracy are important, and can't simply be brushed aside," he said at the close of the Summit.

Mr Obama's comments tempered speculation that a historic thaw in relations between the US and Cuba was on its way following conciliatory gestures by the two countries.

Mr Obama and Cuban President Raul Castro in recent days said they were willing to open talks on such hot-button issues as political prisoners and human rights.

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