Pope John Paul II's unexpected announcement last week that 1983 would be an Extraordinary Jubilee or Holy Year, the second in eight years, came as a surprise to most churchmen here but appears to have gladdened many a Catholic heart.

Since 1425 the Roman Catholic holy years have been held every 25 years. But several popes have called Extraordinary Jubilees as well. The last Extraordinary Holy Year was held in 1933 to celebrate the 1900th anniversary of the redemption of Christ. Pope John Paul has called a holy year for 1983 to celebrate the 1950th anniversary of that Christian event and has named it the "Holy Year of the Redemption," raising questions in some Catholic quarters as to the political or financial motivations behind it.

Outside the Vatican, however, the unexpected proclamation has met with mixed reactions. The city's leftwing municipal administration is concerned that the onslaught of unexpected visitors will severely strain the city's resources and bring a questionable financial return.

"We can expect to have some difficult months," said Bernardo Rossi Doria, the city's commissioner of tourism. "There will be a lot of problems," he added, "but our major task will be that of trying to keep Rome from turning into a gigantic bazaar."

Last Saturday, the day after the pope's announcement, Communist Mayor Ugo Vetere and other local officials met with Vatican authorities to discuss the practical problems posed by the new Holy Year.

"They took us by surprise," said Vetere. The city has less than three months to prepare until the day in February, probably Ash Wednesday which this year falls on Feb. 16, when the pontiff will symbolically open the sealed holy door of Saint Peter's Basilica with three taps of a silver hammer to signify the beginning of the Holy Year.

For the 1975 Holy Year, when an estimated 8 million pilgrims from 58 countries flocked to Rome for the religious celebration, preparations began in 1973. Even then there were so many problems that Pope Paul VI later complained that "the Roman Church and the Catholic world expected something more from the Italian side."

Next year's celebration could bring as many as 18 million pilgrims to the city, Italian newspapers have calculated, at a time when Rome is planning major renovation projects in the downtown area that are bound to create logistical problems. The city will begin work early next year on a controversial plan to tear up a major street near the Roman Forum and build a giant archeological park, and to create a vast pedestrian mall that will also cause traffic to be rerouted.

City officials said that traffic around Saint Peter's Square is already paralyzed by cars and tour buses on Wednesdays when the pope holds his general audiences and on Sundays when he makes his weekly address.

The second line of the still-unfinished Rome subway has been completed since 1975, but promised car and bus parks on the city's outskirts have yet to be built.

The pilgrims are also expected to strain the understaffed museums and monuments, overcrowded hospitals, and narrow sidewalks.

For Rome's shopkeepers and merchants, the holy year is thought likely to bring a welcome uplift, even though Paolo Sesini of the Bar and Cafe Owners' Association said "in 1975 much of the financial benefit went to the religious circuit." There is also some pessimism among the managers and owners of Rome's 1,200 hotels and pensions, which offer 62,000 beds a night. In 1975, thousands of pilgrims were put up at lower rates by the city's convents and religious institutes.

The Holy Year, a Roman Catholic tradition with roots in the Hebrew jubilee custom, dates back to 1300. The first was established by Pope Boniface VIII who reportedly sought to bring crowds to Rome for that year's papal indulgence.

The indulgences -- the sale and purchase of which were a key complaint of Martin Luther in the 16th century Reformation -- often made holy years controversial. Holy Year still comes under some internal criticism among Catholics.

Pope John Paul said he decided to hold the special celebration on purely religious grounds, but skeptics offer other theories. Some believe the pope sought a reason to have a holy year before the scheduled date of 2000 when he would be 80.

Others say that the operation, which brings in money both to the Vatican and its religious orders, is a good way to help close the Vatican's yawning deficit.