The government of US President Barack Obama, however, has made it clear that no significant progress will be made in these talks until the release from prison of US contractor Alan Gross, who was arrested in Cuba more in December 2009.

No formal charges have been pressed against Gross, 62, so far. Cuban authorities have accused him of distributing satellite communications systems on the island, where they are forbidden. According to US sources, he intended to facilitate Internet access for Cuba's Jewish organizations. Havana calls him a spy and says the case is still 'under investigation.'

This is the fourth immigration meeting of its kind between the United States and communist Cuba. Talks were relaunched in 2009, after Obama was inaugurated, after a six-year pause. The third round of negotiations took place in Washington in June.

Cuba and the United States signed a migration agreement in 1994, in the wake of the so-called Balsero Crisis, when thousands of Cubans reached US shores on precarious rafts and boats.

Since then, the United States has agreed to grant 20,000 visas per year to Cuban citizens, while Cuba takes back without retaliation those who are sent home by US authorities.

Based on the 1966 Cuban Refugee Adjustment Act, any Cuban citizen who reaches US soil is granted refugee status. If aspiring Cubans are found by the US Coast Guard at sea, however, they are sent back, in what is known as the 'Wet Foot, Dry Foot Policy.' Cuba demands that this law be repealed, as a precondition for a new immigration deal.