U.S. President Barack Obama promised one of Cuba's most prominent dissident groups he would raise the issues of freedom of speech and assembly with Cuban President Raul Castro during his March 20-22 visit to the Caribbean island.

In a letter dated March 10, Obama praised the work of the Ladies in White, which marches weekly to protest Cuba's Communist government, and defended his policy of seeking to normalize relations with Cuba as good for its people.

U.S. support for the dissidents is a source of tension ahead of Obama's visit, the first by a U.S. president since Fidel Castro's rebels overthrew a pro-American government in 1959.

After more than half a century of Cold War-inspired animosity, the two sides promised 15 months ago to normalize relations.

The Ladies in White criticized Obama's policy change, saying the Cuban government continues to suppress dissent by breaking up anti-government demonstrations while maintaining a monopoly on the media. They say Cuba has cracked down more ferociously since rapprochement.

"We take seriously the concerns you have raised," said Obama's letter, which group leader Berta Soler read to about two dozen Ladies in White and other supporters gathered in a Havana park.

"I will raise these issues directly with President Castro," said Obama, who called the Ladies "an inspiration to human rights movements around the world."

A senior U.S. official in Washington confirmed that an Obama aide delivered the letter to the Ladies in White in Miami.

As in marches for the most of the last year, a demonstration on Sunday ended with police detaining the protesters after they were met by a larger group of pro-government counterdemonstrators.

Police detained about two dozen people, at which point the streets filled with conga dancers and drummers who led hundreds of government supporters in their own rally. The weekly demonstrations and detentions are normal, but the conga line was an additional flourish a week before Obama's visit.

Soler welcomed Obama's letter but still disagreed with him for enacting unilateral changes without any reciprocal moves by Cuba.

"The response of this letter is positive for us, and we greatly appreciated it," Soler said minutes before she was detained.

The Cuban government dismisses the dissidents as mercenaries seeking to destabilize the country. Cuba also defends its universal healthcare and education as human rights and criticizes the U.S. record on race relations and the Guantanamo Bay military prison.