Cuban Director of the National Centre for Sexual Education Mariela Castro, daughter of President Raul Castro, participates in a march against homophobia on May 12, 2012, in Havana. (AFP/Getty Images)

The Obama administration granted a visa this week to the daughter of Cuban President Raul Castro but rejected visas for nearly a dozen other Cubans to attend an academic conference in California, angering both conservative Cuban American leaders and American scholars seeking to improve U.S.-Cuban academic ties.

Mariela Castro, 50, an advocate for gay rights and a niece of longtime communist leader Fidel Castro, will be allowed to travel to San Francisco next week for a meeting of the Latin American Studies Association, and she will later visit New York, administration officials and several American scholars confirmed Thursday.

The news provoked a flood of condemnation from Cuban American politicians, including several members of Congress, who strongly oppose the Castro government and are wary of rewarding or loosening ties with the island’s communist regime.

In a letter Thursday to Secretary of State Hillary Rodham Clinton, a group of legislators blasted the government’s “appalling decision to allow regime agents” from Cuba to enter the United States. Sen. Robert Menendez (D-N.J.) said advocates of Cuba’s government such as Mariela Castro should not be granted a platform to espouse “twisted rhetoric.”

Among American scholars who specialize in Latin America, the decision to deny visas to other prominent Cubans invited to the conference — including several who visited the United States last year — aroused equally forceful criticism.

“This is arbitrary, shameful and cowardly,” said Philip Brenner, a professor and Cuba expert at American University. “Many of these people are prominent scholars who have a history of advocating improved relations with the United States. All of them have received visas in the past. Why are they now suddenly being turned down on the grounds that they are a potential danger to the United States?”

Ted Piccone, an official in the Brookings Institution’s foreign policy program, said he was mystified by the administration’s criteria in choosing which Cubans may visit the United States. Brookings is hosting a Cuban historian and Communist Party member, Eusebio Leal, at an event in the District on Friday.

“I find it baffling. I wish I knew what their thinking was,” Piccone said. He noted that among the Cubans denied visas was Carlos Alzugaray, a former ambassador to the European Union, who was invited to a meeting at Brookings next week. Another barred figure was Rafael Hernandez, a scholar who has taught at Harvard and Columbia universities.

State Department officials declined to comment publicly on any individual visa decisions, including the reason for admitting Mariela Castro. They noted that under U.S. law, Cubans representing the Havana government or the Cuban Communist Party have been legally banned from the United States since 1985 but that exceptions are often granted on a case-by-case basis.

Officials said about 80 Cubans were invited to attend the conference in San Francisco next week. Of those, they said 41 visas have been approved, 11 have been denied and 25 are under review. They said even if an applicant is granted a visa once, later applications can be refused if new information indicates that person presents a risk.

A copy of one visa denial letter, issued last week and obtained by The Washington Post, stated that Soraya Castro Marino, who directs a study institute in Havana and was a visiting scholar at Harvard in 2010, was found ineligible this time because her presence would be “detrimental to the interests of the United States.” All rejected applicants reportedly received the same letter.

Mariela Castro, who directs Cuba’s National Center for Sex Education in Havana, has become a prominent advocate for gay rights. Although detractors see her as a mouthpiece for the government, others see her in a more favorable light.

“She is a champion for human rights. She is not a critic of the regime, but she is an outspoken critic of its policies,” Brenner said.

The secrecy of the visa process and the apparent contradictions in how applicants are judged make the system vulnerable to charges of political ma­nipu­la­tion. Some critics suggested Thursday that the criteria for granting Cubans visas may have more to do with the shifting mood in Washington or Havana than with an applicant’s merit.

State Department officials said they would process the remaining Cuban visa applications in the next several days.