The United States Thursday welcomed the surprise release from prison of Cuban dissident Marta Beatriz Roque, one of 75 opponents of the Fidel Castro government jailed in a widely-criticized political crackdown last year.

Ms. Roque, an economist, was the only woman among the 75 dissidents sentenced to long jail terms last year, and the United States had made repeated calls for her release on health grounds.

Serving a 20-year prison term, she is understood to have been suffering from heart problems and diabetes.

Her release, confirmed by family members in Havana, was welcomed by State Department spokesman Steven Pike, who said the 59-year-old Ms. Roque should never have been imprisoned in the first place.

"Like many other prisoners of conscience held in Castro's Gulag, she suffered from inadequate medical care in prison," he said. "Typically, the Castro government has once again released an activist only when her deteriorating health became and inconvenience."

Ms. Roque and her fellow activists were convicted of subversion and other charges in a rapid series of trials in April 2003 for allegedly conspiring with U.S. diplomats in Havana against the government.

She is the seventh of the dissidents jailed in last year's crackdown to be released for health reasons in the last few months.

However, spokesman Pike said Cuban authorities have escalated harsh treatment of other prisoners including physician Oscar Elias Biscet, about whom the State Department issued a statement of concern earlier this week.

The statement said Dr. Biscet, an advocate of non-violent resistance to the communist government serving a 25-year-sentence, had been put in solitary confinement.

It said authorities had barred his wife from bringing him supplementary food and medicine that other prisoners depend on, and had knowingly done this while Dr. Biscet's health has deteriorated markedly.

Spokesman Pike said the United States repeats its call on the Cuban government to release all political prisoners immediately, and to allow humanitarian organizations to monitor prison conditions.