Fifty years after the Cuban missile crisis, Havana remains virulently hostile to the United States, which reciprocates by maintaining a crippling economic embargo against the communist-ruled island.

Despite the passage of time, official speeches from the Castro regime and state-controlled media still refer to the superpower 90 miles (145 kilometers) across the Florida Strait as "the enemy" or "the Northern empire."

The "blockade," as Cubans describe the US economic and financial embargo imposed by Washington since February 1962 before the Missile Crisis, remains the main obstacle to any normalization.

Fidel Castro suffered a health crisis in 2006 and delegated duties to his brother Raul. Despite some loosening of rules on property ownership and business, the regime has kept a strong grip on the reins of power.

Cuban officials insist that the embargo, enshrined in US law and condemned annually by an overwhelming majority of UN members, has already cost this island nation of 11 million people more than $100 billion.

"It is the main cause of our country's economic woes," Cuban Foreign Minister Bruno Rodriguez said on September 20.

In addition, since 1982, the US State Department has added Cuba to its list of "state sponsors of terrorism," alongside Iran, Syria and Sudan.

The US naval station at Guantanamo, under "perpetual lease" since 1903 in the southeastern corner of the country, is also a painful affront to Cuban nationalism.

In 1962, the end of the embargo and the return of Guantanamo were already two key demands by then Cuban leader Fidel Castro for a withdrawal of the Soviet missiles, deployed at the height of the Cold War.

The Soviet deployment was in response to the stationing of US intermediate-range missiles in Britain, Italy and Turkey capable of striking Moscow with nuclear warheads.

In recent years, Washington and Havana have found new bones of contention, with the Cubans routinely denouncing "the unjust" detention of five of their agents arrested in 1998 after they had infiltrated anti-Castro groups in Miami.

To counter the demand for the release of the five, hailed in Cuba as "heroes of the anti-terrorist fight", Washington has been pressing Havana to free detained State Department contractor Alan Gross.

Gross, who is 63 and may have cancer, was arrested in 2009 and is serving a 15-year sentence for illegally providing satellite phone and computer equipment and service to members of Cuba's Jewish community.

But despite the chill, the two countries maintain ties.

The embargo has not prevented the United States from being Cuba's seventh largest trading partner, mainly thanks to export waivers extracted by the powerful US agribusiness sector.

Although diplomatic relations were broken off in 1961, the United States maintains an "interests section" housed in the Swiss embassy, the largest diplomatic contingent in Cuba.

Havana charges that the US interests section's main mission is to bankroll what it describes as the "mercenary" domestic opposition.

Over the past five decades, hundreds of thousands of Cubans have emigrated, most of them to the United States, now home to 1.5 million Cubans and their descendants.

While the first waves included mainly "political" exiles, they were later followed by thousands of Cubans fleeing essentially for economic reasons and who maintain family ties in their homeland.

And Washington spurs the exodus by delivering 30,000 annual visas each year to Cubans, including many young graduates, a practice frequently denounced by Havana.

Without the $2.5 billion in annual remittances sent by these US-based exiles to their relatives on the island, many Cubans would find it hard to make ends meet, given that the average monthly salary is officially a paltry $19.

Last year, an estimated 400,000 Cubans Americans visited Cuba, each instilling a bit of US culture, especially among the young.

"If politicians from both countries refuse to change their policy, these people-to-people exchanges will eventually lead to warmer bilateral ties," a western diplomat, speaking on condition of anonymity, told AFP here.