An American delegation to an academic conference in Havana was prevented from travelling to Cuba by the United States government.
The seven-member delegation planned to attend the international conference on operations research at the University of Havana, where they had also been asked to help establish a graduate school of management.
"It's not like we were going down there to endorse the opposite (political) system," said Ralph Steuer, a professor of business management at the University of Georgia, who was to be the keynote speaker at the conference.
Dr Steuer and his six colleagues did not receive the licence the American government requires for its citizens to enter Cuba. A spokesman for the Treasury Department, whose job it is to review applications, said the group had failed to submit all of the required documentation but declined to be specific.
Dr Steuer said: "They're just stonewalling. This really gets to the free flow of information and free travel, which I always thought was one of our principal values. The academic community in particular ought to be encouraged to have this kind of interaction."
Americans may travel to Cuba, but spending dollars there is banned. Exceptions include government officials, journalists and members of international organisations on formal business. There also are vaguely worded exemptions for educational and cultural exchanges.
Dr Steuer said some US universities, including Georgia, are trying to establish links with Cuban counterparts in anticipation of the potential democratisation of Cuba.