Cuba is bracing for the possibility of the United States breaking off diplomatic ties but will seek to maintain them nonetheless, Havana's top diplomat in charge of relations with Washington told AFP.

"We must be aware that this can get worse," said the official, Carlos Fernandez de Cossio, summing up months of mounting tension between the two countries.

The reason for the downturn in relations -- five years after an historic thaw between the Cold War foes -- is simple, he said in an interview with AFP.

"Those in charge of US policy towards the Western Hemisphere have attitudes and positions that are extremely aggressive towards our country."

"We are seeing that what they want to do is to break all the exisiting links, to close the embassies," he said.

"We hope that this won't be the case but we cannot trust that this will not happen," said Fernandez de Cossio, director general of the US desk at Cuba's foreign ministry.

"We are prepared, ready for such an eventuality but we do not wish it."

The embassies were reopened in 2015, months after US President Barack Obama and Raul Castro agreed to revive diplomatic ties severed since 1961.

It was a shining moment that drew a line under nearly six decades of Cold War rivalry, and promised a new era of openness.

"It was an emotional moment for the Cuban people," said Fernandez de Cossio, recalling the hope that prevailed in his country at the time.

But five years on, he has mixed feelings about the progress made.

The first two years were unremittingly positive: travel and trade restrictions were eased, a direct telephone link was restored, and Obama visited Havana.

But then it all changed with the arrival of President Donald Trump in the White House.

Carlos Fernandez de Cossio, Havana's top diplomat in charge of relations with Washington, recalls the "emotional moment" and hope in Cuba after US President Barack Obama (L) and his Cuban counterpart Raul Castro (R), agreed to revive diplomatic ties
Carlos Fernandez de Cossio, Havana's top diplomat in charge of relations with Washington, recalls the "emotional moment" and hope in Cuba after US President Barack Obama (L) and his Cuban counterpart Raul Castro (R), agreed to revive diplomatic ties AFP / NICHOLAS KAMM

"In the last three years, there has been a gradual erosion (of the relationship) until the current moment when the US government is clearly declaring its aggressive intent towards Cuba."

As long as Washington maintains an economic embargo, which Obama failed to lift during his presidency, "it's very difficult to think seriously about sustainable progress in the bilateral relationship."

Right now "it's at a very low point," Fernandez de Cossio said, citing what he called the "drastic" US measure of depriving 11 million Cubans of fuel by targeting shipments from ally Venezuela with sanctions.

He also pointed to Washington's criticism of Cuba's foreign medical aid program under which it sends thousands of doctors abroad. That criticism, he says, "is an extreme which no American government has ever reached before."

The US has focused its ire on Cuba over two issues: its human rights record and its support for Venezuela's socialist President Nicolas Maduro.

Fernandez de Cossio dismissed the human rights criticism as "a pretext, totally hyprocritical" given that Washington sponsors "the most brutal regimes on the planet."

The Cuban government has always refuted the existence of political prisoners on its soil, estimated at around a hundred by various NGOs.

"Anyone who says or thinks that Cuba supports the Venezuelan government is absolutely right," he said, as the two countries are long-time allies.

"But it is wrong to say that Cuba has a military contingent of 25,000 soldiers in Venezuela" -- dismissing a US assertion about the extent of its military involvement in the country.

The Cuban diplomat said he isn't holding out much hope that the upcoming US elections will change anything.

"Nobody knows what will happen in 2020 in the United States."

But "Cuba has historically shown its wish for, and remains willing to build, a respectful, civilized relationship with the United States," he said.

In that sense, "the Democratic presidential candidates all seem to be leaning, at least publicly, in favor of the resumption of the policy initiated by the government of Barack Obama, and this can be a sign of hope."