By NINA BERNSTEIN
 
The Bush administration has denied entry to all 61 Cuban scholars scheduled to participate in the Latin American Studies Association's international congress in Las Vegas next week, deeming them "detrimental to the interests of the United States."

The last-minute move, which comes on the heels of new restrictions on travel by Americans to Cuba, is provoking anger and dismay among leading American academics, who called it an unprecedented effort to sever scholarly exchanges that have been conducted since 1979.

Darla Jordan, a spokeswoman for the State Department, said that the decision reflected the stricter policies toward Cuba announced last year by President Bush as a strategy to hasten the end of Fidel Castro's government. Citing 68 members of the opposition in Cuba who remain in prison there after being arrested in 2003, she said, "We will not have business as usual with the regime that so outrageously violates the human rights of the peaceful opposition."

But organizers of the conference, to be held next Thursday through Saturday, said they learned of the denial only on Tuesday, after months of assurances by State Department officials that the visas were on track. Those rejected include poets, sociologists, art historians and economists, among them a professor who was a visiting scholar at Harvard last fall and others who have frequently lectured at leading American universities.

"This is attacking one of the fundamental principles of academic life in the United States, which is freedom of inquiry, " said Marysa Navarro, a historian at Dartmouth who is president of the association, the world's largest academic organization for individuals and institutions that study Latin America. "I asked when was the decision made, and I was told that it was very recent and it was very high up, so it was either the secretary of state or the White House."

"It's an election year," she added, "and I think we're being held hostage to satisfy that sector of the U.S. electorate which is against any kind of relations with Cuba."

The Bush administration has undertaken tough measures against Cuba in the pre-election season that administration officials say are intended to help establish Cuba as a democratic free-market state. But critics say the measures are chiefly devised to strengthen the incumbent's backing among Cuban-Americans in Florida, a swing state.

"Restricting access of Cuban academics to the United States is consistent with the overall tightening of our policy," Ms. Jordan said, noting that Cuban academic institutions are state run. "Our policy is not about restricting academic exchanges or freedom of expression. It is the Castro regime that does that through its restrictive issuance of passports and exit permits only to those academics on whom it can rely to promote its agenda of repression and misrepresentation about Cuba and the United States."

But this characterization of the invited Cuban academics was angrily rejected by John Coatsworth, director of the David Rockefeller Center for Latin American Studies at Harvard. "I can tell you with a certainty that that's a lie," Professor Coatsworth said, noting that among the scholars denied visas are five contributing authors to a book on the Cuban economy in the early 20th century, which the center is publishing next month.

He said that one, Omar Everleny Pérez Villanueva, who was a visiting scholar at Harvard last fall, even wrote his dissertation on the benefits of direct foreign investment in Cuba.

"They are honest, they're courageous, they do superb work," Professor Coatsworth said. "These are the kind of people who let the Soviet Union become Russia. This policy of restricting people-to-people contacts only benefits those who would benefit from violent change instead of a peaceful transition."

Professor Navarro said that the United States had not imposed blanket restrictions on scholars from other countries where political dissidents are jailed. Among the presenters at the conference are four scholars from China who apparently had no difficulty with visas, she said.

Though 75 percent of the association's 5,000 members live in the United States, its international congress, held every 18 months, draws participants from all over the world. Forty-five sessions out of 600 will have to be canceled, organizers said, including panels on contemporary Cuban poetry, gender in Cuban literature, and Cuban agriculture.

The message it confirms to the rest of the world, said Kristin Ruggiero, a historian who directs the Center for Latin American and Caribbean Studies at the University of Wisconsin, Milwaukee, "is that the borders are closing."