"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 signaled a historic shift in US ties with Cuba, ordering his administration to initiate steps to normalize relations.
The State Department must also study the prospects of lifting communist-run Cuba from the list of states that sponsor terrorism.
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, Psaki said.
Senior officials from both countries are due to meet to start the process of normalizing ties in Havana later in January. An exact date has not been set.