The Roman Catholic archbishop of New York crossed the Green Line into west Beirut today to meet with Lebanon's highest spiritual Moslem leader, but later he said inquiries about the fate of five missing Americans and other western hostages had led nowhere.

Escorted by five van-loads of Lebanese policemen and a Range Rover bristling with Lebanese security men from the U.S. Embassy, Cardinal John O'Connor arrived in one of two black limousines flying the flag of the Vatican.

He was accompanied by the papal nuncio in Lebanon, Luciano Angeloni, and other Lebanese clerical figures in the Moslem-controlled western sector. The cardinal met with the Sunni Moslem mufti of the republic, Sheikh Hassan Khaled, at his home in Ramlet al Baida, about a mile from the embattled Palestinian refugee camps in Beirut's southern outskirts.

A weekend cease-fire between Palestinian guerrillas and Shiite Moslem militiamen was broken this afternoon as rocket and machine gun duels raged only minutes before O'Connor's convoy crossed from the Christian half of the Lebanese capital.

Earlier in the day, seven Christians, four of them printers at the independent An Nahar newspaper, were kidnaped by unknown gunmen as they took the same route.

O'Connor told reporters following his one-hour session with Khaled that wherever he went during his three-day visit here he sought "information or help in regard to the hostages." The cardinal added that he was not able to convey messages to the hostages.

"I bring them messages from their families, and I bring love from their families. I had talked with their families back in the United States but, unfortunately, no one has been able to make it possible that I would be able to get that word to them," O'Connor said.

The cardinal, who arrived here Saturday, met with President Amin Gemayel and visited centers for the handicapped and Lebanese refugees in Christian areas. He said his visit here was "purely pastoral," but he offered to help in efforts to gain the release of the Americans kidnaped in Moslem west Beirut and other foreign hostages.

He expressed hope that "merely inquiries" and messages through the media would reach the hostages and "tell them not to lose heart, that we are still praying for them and hoping for their safe return."

O'Connor said he sympathized with a black-clad Lebanese woman who approached him as he left the mufti's house and identified herself as the wife of a Lebanese Christian worker who was kidnaped by Moslems in 1982.

She told O'Connor she had come to represent the families of 2,111 missing Lebanese kidnap victims.

"We also have from the United States some who have been kidnaped," he told her slowly as a deputy of the Christian Maronite patriarch, Monsigneur Roland Abu Jawde, translated. "I wish that we could have them back with us."

O'Connor, scheduled to leave Tuesday morning, said meetings with other Moslem figures from the Shiite and Druze communities could not be arranged. He said he hoped he would return to Lebanon and "meet with them at a later date."