Pope John Paul II has warned that the increasing difficulty of recruiting men to join the Catholic priesthood in the US represents a "stark challenge".
The Pope said Bishops should pray for an increase in vocations
The Pontiff said the problem must be urgently addressed and suggested one day each year should be dedicated to praying for vocations.
He said the church must guarantee its future by preserving existing faith and encouraging new belief.
Several sexual abuse scandals have hit already dwindling US priest numbers.
"No-one can deny that the decline in priestly vocations represents a stark challenge for the church in the United States," Pope John Paul II told American bishops gathered in Rome.
"And one that cannot be ignored or put off."
"I would propose for your consideration that the Catholic community in your country annually set aside a national day of prayer for priestly vocations," he added.
In a report earlier this year, the Vatican said the total
number of priests had fallen sharply in North America and Europe
between 1961 and 2001.
In North America, the number dropped from 71,725 to 57,988 at a time when the population was growing.
Numbers have been further weakened by allegations of US priests' involvement in child abuse scandals, which surfaced in January 2002.
Many dioceses have been forced to declare themselves bankrupt because they cannot afford to meet the claims of all those who say they were abused.