American churchmen who held tearful Christmas services for the hostages in the occupied U.S. Embassy early today said in a report on their overnight visit that they could account for only 43 of the 50 Americans believed to be in Iranian hands.

The three clergymen said this afternoon that those hostages they saw appear to be in good physical condition, although some show signs of stress after seven weeks of capitivty.

The observation of the clergymen provided the most extensive impressions so far of how the American hostages have been faring since the embassy was taken over Nov. 4, but their tally of the number of Americans they saw only compounded the already bitter dispute over the number being held.

"Throughout the time I was with the hostages, we sang together, sprayed together and we shared the eucharist together," said Catholic Auxiliary Bishop Thomas J. Gumblton of Detroit, one of four clerics allowed inside the embassy. "I should also say we wept together."

In general, the clergymen avoided going into detail and sought to reassure families of the hostages that they saw no signs of physical abuse and that the prisoners they saw are no longer bound. At the same time, they reported that the strain of 51 days under the gun of the Iranian militants showed among some captives, particularly the younger ones, and that some apparently still are held in solitary confinement.

"As far as we could tell -- and on the physical side you can tell -- they are in good shape," said the Rev. William Sloane Coffin, of the interdominational Riverdale Church in New York City. The former anti-Vietnam war activist added that "they do look well. Some of them bear dentention better than others, but that is to be expected."

Coffin and Gumbleton spent five hours with the hostages, as did the Rev. William Howard, president of the National Council of Churches, and Cardinal Leon-Etienne Duval, archbishop of Algiers.

The four negotiated for two hours with the student militants before the Christmas service began. In the end, the visitors were tightly controlled and only saw the hostages separately in small groups, always with a student guard and Iranian television cameraman. Non-Iranian journalists were not allowed in the embassy for the occasion.

The clerics, after comparing tallies early today, expressed the belief that they saw a total of only 43 hostages. The State Department has said the students hold 50 hostages in the embassy in addition to three Americans in custody at the Iranian Foreign Ministry.

Coffin and his American colleagues, who reported on their visit after consulting among themselves, declined to speculate on the discrepancy, saying only that the students had told them they would not be allowed to see "all the hostages." Duval made no report on his impressions.

A student reached by telephone inside the embassy confirmed today that there are 50 hostages in all and suggested the seven who were not seen "could be agents." This raised the possibility that, in spite of their pledge, the students held back those they suspect of espionage. There also have been persistent reports that some hostages have been taken out of the embassy and transferred elsewhere in Tehran.

Observers who have been in frequent contact with the students noted, however, that comments to inquiring reporters often are contradicted by someone else who answers the embassy telephone several hours later. A second student asked today about the difference in numbers said only: "There might have been a mistake." A third put the number of hostages at 49.

The churchmen said they will try to compile a list of names of those they saw, but an aide to the group, Warren Day, said they had not written down the names of those inside the embassy during the night and would have to rely on memory for comparison to phottographs.

They confirmed, however, that one black hostage was among those seven. Charles Jones of the International Communication Agency has been identified as the only remaining black prisoner since the other black hostages were released.

The clergymen entered the embassy in downtown Iran shortly after 11 p.m. yesterday with the intention of conducting a joint ecumenical service. Despite two hours of arguing with the students, they were forced to change plans and see small groups of hostages in different rooms.

Coffin said he saw 16 prisoners in four groups of four. Gumbleton and Duval said together they saw one group of four men and another of two women -- apparently Katherine Koob of Fairfax, Va., and Elizabeth Ann Swift, previously identified as the only remaining women hostages.

Howard said he saw four groups of four and one of five, for a total of 21. All seemed well fed and dived with gusto into the Christmas cookies and candy brought into the embassy, he said.

The hostages appeared alert and inquired about which football teams were in the professional playoffs and college bowls, he said, but they also complained that they have not been hearing from their loved ones in the United States. This seemed to contradict statements from their student captors that mail is being distributed to the prisoners.

"Virtually all hostages who spoke about this said they have not been receiving mail," Howard said.

All three clergymen described emotionally charged moments despite the student guards, cameramen and the splitting up into small groups.

Coffin said even one of the rifle-toting student guards had tears in his eyes at one moment in the ceremony "I am sure we brought the hostage some small measure of comfort," he said. "This obviously is one of the most moving Christmases I have ever had. There were tears in our eyes."

Coffin said tension is high within the embassy even after seven weeks of occupation because the Islamic militants as well as some of the hostages still fear the possibility of a military rescue operation by the United states.

The strain, he said, is telling on some hostages. The anguish is particularly apparent on younger ones, he added, without naming them.

"The oldest hostage, Mr. Ode, he seemed to be bearing up fairly well, but, you know, there's tension in there," Coffin said. "They feel there might be some kind of rescue mission."

Robert Ode, 62, of Falls Church, Va. has been identified in news reports as one of the hostages.

The fear of attack apparently underlies the extraordinary security precautions taken by the students and their refusal to allow the clerics to see the hostages all at once. At the same time, Coffin said the leadership inside the embassy seems to feel that any hostages deaths or injuries would mean the end of their pressure on the United States, presumably because it would invite retaliation and explode the currently peaceful standoff between Tehran and Washington.

"They are intensely conscious of the fact that nothing must happen to a single hostage or they have failed," he said.

Bumbleton protested two "political statements" by a student spokesman and the filming of four male hostages during his visit. This violated the pastoral spirit of the services and transformed then into a political gesture, he complained.

After negotiations with the militant students later today, the clerics were authorized to pick up personal messages from the captives for relay to their families in the United States.

The churchmen are to meet Foreign Minister Sadegh Ghotbzadeh on Wednesday in an effort to expand their visit to include an attempt to free the prisoners. There was no hint in the embassy that an early release is planned, Coffin said, adding that he had a clear impression that the students are reluctant to take orders from the government anyway.

"They run their own show," he said.