WASHINGTON (AFP) - Cuba has freed some of the 53 political prisoners identified on a US list as it moves towards normalizing ties with the United States, an American official said Tuesday.

"They have already released some of the prisoners," State Department spokeswoman Jen Psaki told reporters.

"Obviously we would like to see this completed in the near future."

She refused, however, to specify how many people were freed.

Last month, US President Barack Obama signalled a historic shift in US ties with Cuba, ordering his administration to initiate steps to normalise relations.

He also wants to eventually persuade Congress to lift the 54-year-old US trade embargo on Cuba which he has described as "self-defeating."

But critics have raised concerns about continuing abuses of human rights by the communist authorities on the Caribbean island.

"This list is not to be seen as the end of our discussion on human rights with the government of Cuba," Ms Psaki stressed.

She pledged top US officials would raise the issue when they meet later this month with Cuban counterparts in Havana for the start of talks to reopen ties.

Havana has also vowed to both Washington and to the Vatican to release the prisoners, she said.

The Holy See played a key role in the negotiations which led to last month's release of US citizen Alan Gross and a Cuban imprisoned for more than 20 years after spying for Washington.

As part of the deal, Washington has presented a "carefully put together" list of 53 political prisoners which the United States would like to see freed by Havana, Ms Psaki said.

"We've been very careful about discussing these prisoners in this process, because we're not looking to put a bigger target on Cuban political dissidents," she insisted.

"We're looking to get them released, and this is the process that we think will be most effective."

An exact date for the Havana talks has not been set yet.

Ms Psaki stressed, however, that the talks were not contingent on the release of all the prisoners.

While the prisoner release was important, "having a dialogue, opening up access to be able to communicate, to organise, those are all steps we feel is important," she said.