Mr. Sánchez, who is among the dissidents expected to meet with the president on Tuesday, said that in the first two weeks of March, 526 critics of the government had been detained. While dissidents are often held for a few hours for printing fliers, staging street protests or just planning them, he and others said Mr. Obama’s visit had set in motion a broader campaign.

On Saturday, Mr. Sánchez himself was held for three and a half hours at the Havana airport. He said he had been separated from his wife; sent to a cold, windowless room; and told that he was not being “detained” but rather “retained.”

“Can I make a phone call?” he said he had asked, as officials made copies of every document in his bag. “No,” came the reply.

“It’s the climate of intimidation the government is creating for Obama’s visit,” said Mr. Sanchez, a graying, steady critic of President Raúl Castro’s government. “Right now what you see is preventive repression, so it does not occur to anyone to say anything to Obama while he is here.”

For decades, Cuban officials have treated every interaction with the United States as a test of sovereignty, and their approach to Mr. Obama’s visit is partly an effort to project competence, confidence and a new commitment to a calibrated friendship.