Each year the gap widens: fewer priests are available to serve an increasing number of Roman Catholics in the United States.

Since 1966, the number of men seeking the priesthood has plummeted from 48,000 to 7,500. By the year 2000, according to surveys produced for the U.S. Catholic hierarchy, the projected decline from resignations, deaths and fewer ordinations will leave only 15,000 active parish priests - about the same number as in 1925 and less than half as many as in 1966 - to serve an estimated 65 million faithful.At the turn of next century, the average age of these priests is projected to be 65.

"The vocation shortage is long-term, not just temporary, and the church is powerless to reverse . . . the social pressures causing the downturn," declared Dean Hoge, a professor of sociology at the Catholic University of America in Washington.

This shortage of shepherds for a growing flock has already made a sharp impact in most dioceses. One in 10 U.S. Catholic parishes has no regular priest. In Chicago, the vocations director fears that the present average of two priests per parish in the archdiocese will slip to only one by the year 2000.

In response to the shortage, the church is training deacons and lay men and women to do tasks formerly reserved for priests. At the same time, the effort to find priests is focusing on candidates from the growing Latino and Asian Catholic populations. Some dioceses are also using novel recruitment approaches, such as advertising for priesthood candidates in national magazines.

But despite the bleak vocations picture, the church has no nationally coordinated program to reverse the trend. And there is no movement at the Vatican to consider changing the celibacy requirement for priests that is the main obstacle for candidates.

A recent Vatican report on college-level seminaries frankly acknowledges that "pressures on the family, the attraction of material prosperity and social comfort, the sexual revolution and the growth of insecurity, as well as a delay in the age of personal career decision-making, have all had their effect."

Indeed. Consider:

-Within 25 years of their ordination, 42 percent of all U.S. priests have resigned. Younger priests are resigning in greater proportion than older ones.

-One of every six men who were ordained as priests are now married, thus eliminating them from priestly service. Of those under age 50, one of every three is married.

-Overall, Catholic seminaries are replacing only about 60 percent of the priests who resign, retire, are disabled or die.