ATLANTA, NOV. 28 -- Federal authorities toughened their stance today toward more than 1,000 Cuban inmates who have held the federal prison here for six days, announcing a cutoff of their water supply and pressing them to unite their diverse factions.

Arms-length negotiations continued off and on through the day, but with no apparent progress. The inmates continue to hold 94 hostages.

Justice Department sources said on-the-scene negotiators were under strict orders to promise nothing on the inmates' major demand -- to remain in the United States -- beyond the offer made Monday by Attorney General Edwin Meese III.

Meese offered a moratorium on deportations and a case-by-case review of each inmate's immigration status.

Negotiators have latitude on such matters as disciplinary action involving the takeover.

The uprising began Monday, two days after Cubans rioting began in Oakdale, La. Both incidents were sparked by the announcement of a revived agreement with Cuba to return about 2,500 of the 125,000 refugees who came to the United States in the 1980 Mariel boatlifts, named for the Cuban port where they originated.

A Justice Department official said a near-agreement Thursday night fell apart when inmates became suspicious that the detainees both here and in Okdale had been led to believe that the other group was about to settle.

"They were requesting that a direct phone line from Atlanta to Oakdale be installed," the official said. The request was denied, and the Oakdale detainees decided independently not to sign an agreement to end the takeover there.

Three more inmates surrendered to authorities today, including one whose foot had been wounded in a knife fight. A total of 272 Cuban inmates and 175 American inmates have surrendered since the takeover, leaving 1,222 Cubans and 20 Americans in the prison.

Authorities said they had did not know why the 20 U.S. citizens remained behind and that none of them had any contact with prison officials.

The water cutoff was partly symbolic because the increasingly organized inmates apparently have some remaining water, and enough food to last "several weeks"

Justice Department spokesman Thomas M. Stewart said the water cutoff had taken place on Friday, but it was not announced until today.

Stewart had signaled a tougher line that day, saying that officials were frustrated and were taking a "firmer posture" in their dealings with the detainees.

But the inmates apparently had some access to water -- what remained in pipes and perhaps from stockpiles stored in anticipation.

In a Spanish-language two-way-radio transmission today, an inmate was heard to say, "Hospital to Control, they promised me in the kitchen they were going to send me two tanks of water, but they haven't."

At midmorning, an inmate was overheard calling for food for himself and a hostage.

"Why," the radio control base answered.

"The pig's hungry," the inmate said.

"We'll bring the pig some food at noon," came the reply.

Although there were indications that the Cubans continued to be split into factions, there were also clear indications that they had organized more tightly, as evidenced by the central radio control base and the addition of a public address system inside one of the prison buildings.

"They can have a town meeting," Stewart said, but he added that prison officials cannot adequately hear the PA system..

Stewart said officials believe that all 94 remaining hostages -- corrections officers and prison staff -- are in good shape. He said it appeared that they had been divided into smaller groups, possibly to make any rescue effort more difficult.

Stewart and J. Michael Quinlan, director of the Bureau of Prisons, expressed frustration with the disjointed nature of the Atlanta talks but said they are prepared to wait for the Cubans to negotiate with one voice.

"They have many proposals coming from many mouths," Stewart said. He added that "when there's an initiation from the detainees, we attempt to get them to be as specific as possible."

But Quinlan said he is setting no deadlines.

"We will wait forever until the hostages are returned safely," he said.

In response to a question, he added, "The attorney general's patience is limitless also."

Another Justice official who asked not to be identified said he feared that misleading inmates that their colleagues were ready to settle had hurt trust in government negotiators.

That may be why government negotiators were willing to consider allowing Auxiliary Bishop Agustin A. Roman of Miami to participate in or witness the talks here. A military plane picked him up in Miami today for the trip to Atlanta but, according to a Justice Department source, was diverted to Oakdale, where the inmates had asked that he witness an agreement for the release of the hostages there.

Early this afternoon, federal negotiators here renewed contact with inmates by telephone.

One detainee reported by radio.

"Santiago," he said to another inmate in Spanish, "the American you talked to last night is here in front of me, and he wants to talk to you."

A third inmate went instead to meet the negotiator near the prison cafeteria. Later, he reported via radio to the inmate's control station on his conversation.

"We are asking for water so that the negotiations can go forward," the inmate said.

Came the response from inmate control, "Food and water are secondary to us. If they want negotiations;, we'll have negotiations. If they have initiatives, we'll hear initiatives."