Former hostage Lawrence M. Jenco, explaining that his public silence was a "shout of fear and concern" for others still held in Lebanon, today delivered a "confidential message" from his Moslem captors to Pope John Paul II during a private audience with the pontiff.

The 51-year-old Roman Catholic priest from Joliet, Ill., who was held in Lebanon for almost 19 months before being released Saturday, told reporters at St. Peter's Square after his meeting with the pope that he had kept "my promise to give a confidential message from my captors to the holy father."

Neither the slight, white-bearded priest nor Vatican officials would elaborate on what was in the message from the Shiite Moslem fundamentalist group Islamic Jihad (Holy War), which continues to hold at least three other Americans and more than a dozen other foreigners in Lebanon.

"Perhaps sometimes I can't answer your questions because I have a fear that what I might say might be detrimental to my brothers who are still held hostage in Lebanon," Father Jenco said in an almost inaudible voice. "My silence really is a shout of fear and concern for those others still held."

Jenco reported today that he had been held captive for part of the time with three other missing Americans: Terry Anderson, 38, chief Middle East correspondent for The Associated Press; Thomas Sutherland, 55, acting dean of the school of agriculture of the American University of Beirut, and David P. Jacobsen, 55, administrator of the American University Hospital in Beirut.

Jenco, who until his kidnaping headed Catholic Relief Services in Beirut, was accompanied by Terry Waite, a special representative of the archbishop of Canterbury, whom Jenco will visit Thursday. Waite has flown to Lebanon several times in the past year to try to arrange release of the hostages.

The 30-minute meeting with the pope was also attended by members of Jenco's family. The priest's relatives had joined him in Frankfurt over the weekend after he was flown there from Damascus, Syria, for medical tests at the U.S. Rhein-Main Air Base.

After the papal audience, Jenco and Waite left for London, where the priest said he would give the same "confidential message from my captors" to Archbishop of Canterbury Robert Runcie.

Following his meeting with Jenco, the pope held a private audience with Bishop Pablo Antonio Vega, vice president of the Nicaraguan bishops' conference, who was expelled from Nicaragua by the Sandinista government July 4 for alleged antigovernment statements.

The pope's meeting with Vega originally had been announced for Tuesday but was canceled without explanation.