By Anthony Boadle

HAVANA (Reuters) - Spain's new envoy to Cuba has criticised the European Union's policy toward the island and said Madrid would work to thaw relations with President Fidel Castro's Communist government.

But Ambassador Carlos Alonso Zaldivar indicated that Spain would not break with the EU's common position on Cuba, which is based on human rights concerns.

"Unfortunately, the current situation of relations between Cuba and Spain, and between Cuba and the European Union, is profoundly unsatisfactory," Zaldivar said in a speech at a diplomatic reception celebrating Spain's national day on Tuesday.

"We want to overcome the present situation, but we want to do that in agreement with the rest of the EU," he said.

Zaldivar regretted the absence of Cuban government officials at the party, which was attended by dozens of pro-democracy dissidents and wives of political prisoners.

Havana froze ties with EU diplomats last year in response to European criticism of a crackdown on dissent that led to the jailing of 75 of Castro's opponents for terms of up to 28 years.

In June last year, Brussels decided to invite leading dissidents to EU national day receptions. Cuban officials walked out and never returned in what has been dubbed the "cocktail war."

Foreign ministry doors remain closed to EU diplomats and their calls are seldom returned.

Brussels insists that Cuba free all jailed dissidents. Havana says they are U.S.-paid agents seeking to destroy its socialist society.

Diplomats from other European nations said recent Spanish overtures to Cuba had been a diplomatic flop.

"For two months they tried to convince the Cubans to be flexible and they have nothing to show for it," said a European ambassador in Havana.

"They have not obtained the release of a single political prisoner. In fact, the Cuban government has set more conditions for unfreezing relations," the diplomat said.