HAVANA -- In an open letter to the foreign press and diplomatic corps, imprisoned dissident Vladimiro Roca asked Wednesday for a ``fair and public trial'' for himself and three other dissident leaders.

The letter, distributed by his wife, Magalys de Armas, came on the eve of the first anniversary of the arrest of the four dissidents for ``investigation of counterrevolutionary activity.'' Formal charges have never been filed.

``We wish to draw public attention to our situation and to demand a fair and public trial, in the presence of the foreign press and any diplomats accredited in Cuba who may wish to attend, in proceedings both transparent and aboveboard,'' Roca's letter said.

``It is not my intention to challenge the authorities or to seek a confrontation, because my position continues to be one of reconciliation, tolerance, forgiveness, reunification of all Cubans and nonviolence,'' the letter said.

In addition to Roca, head of the Social Democratic Party and son of one of the founders of Cuba's Communist Party, the detainees are Martha Beatriz Roque, director of the Cuban Institute of Independent Economists; lawyer Felix Bonne, president of Cuban Civic Mainstream; and Rene Gomez Manzano, president of the independent lawyers group Agramontist Mainstream.

They headed the Domestic Dissidents Working Group, a federation representing 14 of the largest dissident groups in Cuba.

The four were arrested July 16, 1997, less than three weeks after they issued a document critical of the draft manifesto of the Fifth Congress of the Cuban Communist Party, planned for October 1997. The document was titled The Homeland Belongs to Everyone.

The unofficial Cuban Commission on Human Rights and National Reconciliation sided with Roca on Wednesday and asked the government of President Fidel Castro to release the four detainees.

``It is regrettable that, despite the time elapsed and without any convincing argument, the prosecutor's office hasn't even filed the specific charges for which they are being kept in high-security prisons,'' said Elizardo Sanchez, the commission's president.