Havana ? Responding for the first time to international condemnation over an unprecedented crackdown, Cuba’s foreign minister justified severe prison terms handed to at least 57 dissidents, saying his government has the right to defend itself against “mercenaries” who work with U.S. diplomats to undermine the island’s sovereignty.

Felipe Perez Roque said Wednesday that Cuba is “not losing sleep” over the potential political and economic fallout of the summary trials in which opposition activists and independent journalists were sentenced to between six and 28 years in prison. His televised remarks were the first news most Cubans had of the trials, which began last Thursday.

“Our country has had to struggle against the obsession of the U.S. government to fabricate an opposition in Cuba,” Perez Roque said.

“We’ve seen more than 40 years of economic embargo, aggression, armed invasion. … with the Bush administration there has been a leap in hostility against Cuba.”

In videotaped snippets of the trials, prosecutors and state witnesses repeatedly linked the dissidents to top U.S. diplomat James Cason, whom Cuba accuses of financing and stimulating the dissidents’ activities.

“Our patience was exhausted by Cason’s actions,” Perez Roque said. “He is the principal person responsible for what has happened.”

Speaking at the University of Miami earlier this week, Cason said he has met with a broad spectrum of Cubans and dismissed Cuba’s accusations that his interactions are provocations.

“They are, in fact, appropriate and routine contacts with legitimate political actors who enjoy international contacts far beyond the U.S. Interests Section,” Cason said.

On Wednesday, Perez Roque also accused the U.S. Interests Section of drastically reducing the number of immigrant visas approved under migratory accords to “stimulate illegal exits, terrorist actions, and hijackings of boats and planes.”

State Department officials said they were complying with migratory accords and had no immediate response to Cuban allegations.

In the last three weeks, two Soviet-made planes were hijacked to Key West, Fla., where suspects are awaiting trial. Last week, a group of men armed with knives and a gun also attempted to hijack a ferry to Key West. Cuban authorities arrested them after a 40-hour standoff.

Perez Roque denied rumors that some of the convicted dissidents could be exiled from Cuba rather than serving their sentences in the country. He added that Cuba would not consider trading the jailed dissidents for five convicted Cuban spies who have been heralded as heroes in Havana.

Asked whether escalated tensions between the United States and Cuba could threaten the countries’ diplomatic missions, Perez Roque said, “That would be the golden dream of those who conspire against Cuba.”