JAKARTA, Indonesia – A business manager in Hanoi, Pham Hong Son, has spent 42 months in a Vietnamese prison. His crime: downloading an essay titled “What is Democracy?” from a U.S. State Department Web site, translating it and sending it to friends and senior Communist Party officials.

Mr. Son, 36, who worked for a pharmaceutical company, was convicted of espionage in Vietnam after a closed, one-day trial in June 2003. He was sentenced to 13 years, later reduced to five.

“What he did was legal,” his wife, Vu Thuy Ha, 34, insisted in a June interview in Hanoi. She said that her husband was exercising free speech and did not commit a seditious act. “What can anyone do with the translation? What can they do to overthrow the government?”

Last week, the American ambassador to Vietnam, Michael Marine, called on Vietnam to release Mr. Son and four others described as prisoners of conscience. Vietnam has made progress in “collective” human rights such as improving education and reducing poverty, Mr. Marine noted. But it is still intolerant of political dissent, he said.

“History has shown that political and religious freedoms go hand in hand with economic prosperity,” Mr. Marine said in a speech to the American Chamber of Commerce in Hanoi. “The pace and scope of Vietnam’s future success depends on a strong commitment to reform in both of these areas.”

Political analysts and international human rights groups do not know precisely how many prisoners of conscience Vietnam has detained, but American officials said the number of cases they have been able to verify had dwindled in recent years to 10 or fewer.

During the past year, Vietnam has released more than 26,000 prisoners, of whom perhaps 15 were political or religious prisoners, American officials said. The younger ones in particular, such as Mr. Son and Nguyen Vu Binh, who was accused of posting “reactionary” articles on the Internet and of trying to set up a liberal democratic party, remain incarcerated.

The government insists it is not repressing religious or political rights. “Some people may argue that Vietnam does not have freedom and democracy and only has a one-party system. But you know, our ultimate goal is to maintain political stability and serve the interests of the people,” Prime Minister Phan Van Khai said in a June interview. “We do not agree with arguments from the outside that there are prisoners of conscience in Vietnam. We do not have any prisoners of conscience in Vietnam.”

Vietnam last month issued a human rights report in which it promised to respect freedom of expression and promote free use of the Internet. A revised press law in 1999 stated that citizens have the right to be informed, express opinions and provide information without being censored by any organization or individual, it noted.

Nonetheless, America last year placed Vietnam on a list of “countries of particular concern” with regard to religious freedom. Officials expect Secretary of State Rice to decide soon whether Vietnam should remain on the list. Mr. Marine said that although Vietnam has taken steps to expand religious and political space, “there is more, much more, that the authorities can and should do.”