Cyber dissident Nguyen Vu Binh, 35, who was arrested in September 2002, was jailed on espionage charges after
criticising border accords between Vietnam and China, judicial sources in Hanoi said.
"We strongly condemn this harsh sentence," said Adam Ereli, the State Department spokesman.
"We are especially concerned that the Vietnamese Government may have targeted Mr Binh because in 2002, he
submitted written testimony to the US Congressional Human Rights Caucus and the Congressional Caucus on Vietnam."
Binh's treatment clearly violated international standards on human rights and freedom of expression, Ereli said, setting the stage for another human rights row with Hanoi.
Colin Powell is being pressured to
ask Hanoi some tough questions
"We remain concerned, in general, about Vietnam's treatment of dissent," he said. "This is, I would note, the third case that we are aware of this year that has involved an individual who posted his views on the Internet.
"The United States urges the Government of Vietnam to immediately release Mr Binh and all of those imprisoned for peacefully expressing their views, and we strongly urge the Government of Vietnam to put an end to its ongoing repression of peaceful dissent."
Several human rights groups have said that the charges against the journalist arose from a letter he sent to the US
Congressional human rights caucus in July 2002.
Binh has been a consistent critic of Vietnam's communist regime. He left his newspaper in January 2001 after applying to form an independent opposition organization called the Liberal Democratic Party with other dissidents.
"We remain concerned, in general, about Vietnam's treatment of dissent. This is the third case that we are aware of this year that has involved an individual who posted his views on the Internet. "
Adam Ereli, US State Department
He was also behind the proposed launch of an anti-corruption organization, which was rejected by the government.
He crossed the red line by criticizing the border agreements, explicitly accusing Hanoi of ceding land to its neighbour.
Washington and Hanoi have sparred publicly several times in recent months over religious tolerance, and the issue is one of several which have soured a bid by both sides to use expanding trade ties to end the bitterness left over from the Vietnam War.
A recent State Department report found that religious freedom was widespread across communist Vietnam, and grouped the country in a worst offenders' category of totalitarian and authoritarian states which view religious groups as "enemies of the state."
In September, the US Commission on International Religious Freedom (USCIRF), a congressionally mandated rights watchdog, called on Secretary of State Colin Powell to nominate Vietnam as a "country of particular concern" on
freedom of worship a move that could lead to sanctions.
Despite frequently speaking out against Vietnam's record, the US State Department has so far declined to recommend the move.