Cuban cardinal Jaime Ortega, leading the service from an altar on the steps of the cathedral, told the congregation the mass marked the start of preparations for the visit of Pope John Paul in January next year.
``With this celebration we start our preparations,'' Ortega said in his homily to a congregation seated on folding chairs or standing in the small and picturesque square in Havana's old quarter.
The mass marked the important Catholic feast of the apostles Peter and Paul, who brought Christianity to Rome.
Church officials said last week they viewed the fact the open-air mass was permitted by authorities as an encouraging sign the church was achieving more freedom in Cuba.
Ortega echoed this in his homily, saying the pope would bring ``seeds of hope'' for a Cuban church that he described as poor in resources but rich in faith.
The Pope's trip to the Caribbean island, scheduled for Jan. 21-25, was agreed last November at an historic first meeting between the pontiff and President Fidel Castro at the Vatican. That encounter marked a clear improvement in ties between the authorities and the church over the past year.
In the early 1960s after Castro's 1959 revolution, church schools were closed and many foreign priests were sent home. Christmas stopped being a public holiday. Although there is now more tolerance for religion, religious practice is limited to church premises.
Caridad Diego, head of the ruling Communist Party's religious affairs department, was seated at the front of the congregation on Sunday, along with deputy foreign minister Isable Allende and some foreign diplomats.
Cardinal Ortega said the church did not have resources for communication and lacked priests, but was ``rich in humility and perseverance.''
And referring to the island's religions of African origin, he said these were sometimes more folklore than religion. The strongest faith in Cuba, Ortega said, was the faith of (apostles) Peter and Paul.
``Christ, Christ,'' the congregation chanted enthusiastically.
The walls of the square were adorned with Cuban and Vatican flags and a giant portrait of the pope.
Some people carried umbrellas against the strong late afternoon sun, others sought shade under the arches of the surrounding buildings.
Out of respect for the occasion, local authorities banned the sale of alcohol at small cafes in the streets around the square until after the service.
Private enterprise in the cathedral square, normally humming with small stalls selling crafts at weekends, was halted for the mass.
A leaflet distributed by the church sought to explain in simple terms the significance of the papal visit. The pontiff is ``not a tourist'' the leaflet said, ``not a politician...not rightist or leftist, not a magic remedy for all our problems.''
``He does not bring recipes or solutions,'' it added.
20:28 06-29-97