President Reagan dispatched four Airborne Warning and Control System (AWACS) planes to Egypt earlier this week after learning that Libyan strongman Muammar Qaddafi was trying to overthrow the Sudanese government, administration officials said yesterday.

These officials said that Reagan and Egyptian President Hosni Mubarak had detailed knowledge of the plan by Qaddafi to overthrow Sudanese President Jaafar Nimeri in lightning-fast assaults.

In an interview with ABC television news last night, Qaddafi denied that any coup d'etat had been planned. He said that any future revolutions in Sudan would come from the Sudanese people.

The reported Qaddafi scheme, intercepted by Sudanese and Egyptian intelligence, called for Libyan-armed insurgents to assassinate Nimeri and his top aides, seize the airport at Khartoum and then land Libyan combat troops there in American-built C130 transports.

The AWACS monitoring of Libyan fighters and transports was considered vital to stopping the coup attempt before it could be carried out.

AWACS planes not only watched the comings and goings of other aircraft for hundreds of miles around but stood ready to guide Egyptian fighters against Libyan bombers and fighters that reportedly were to attack Khartoum in support of the coup attempt.

The aircraft carrier Nimitz, which had been in the central Mediterranean on an unrelated training exercise, steamed toward Egypt so its planes could back up Mubarak's limited air force in a noncombatant role, such as surveillance, if the Egyptians had to go into combat.

The state-run Sudanese radio reported yesterday that a ring of "subversives" had been broken up and that members had been arrested. U.S. officials pointed to this report as confirmation that the coup had been thwarted.

Qaddafi, who has feuded with Nimeri for years, reportedly sought to take advantage of internal Sudanese turmoil caused by severe economic hardships and the threat of a secessionist movement in the south of Sudan.

There have been fears that civil war could break out and Sudanese officials have charged Libyan agents with fanning the discord.

It was the secret reports of the impending coup that caused President Reagan to be extremely careful about what he said about the situation at a nationally televised news conference on Wednesday, officials said. Reagan referred to the Libyan threat in the most general terms and said there were no U.S. naval movements directed at Libya.

Reagan was described as "angered" by subsequent network reports that he was, as one official characterized it, "either ignorant or lying" about the Libyan military buildup near the Sudanese border or the presence in Egypt of the four AWACS planes.

In fact, administration officials said Reagan had approved the sending of the AWACS planes to Egypt several days before and had been briefed throughout the day on Wednesday about the coup and the maneuvers of the Nimitz.

Reagan also had been told that two Libyan MiG23 fighters had, on Tuesday, approached within 60 to 100 miles of the Nimitz but took no menacing action and may not even have spotted the carrier.

One official who has winced in the past over the president's proclivity for militant rhetoric in crisis situations said that Reagan was "trying to speak softly and carry a big stick."

Ironically, this tactic combined with what one administration official called a "perplexing" White House briefing the following day to cast Reagan as uninformed and out-of-touch with what was going on in Libya.

The president had been told before the news conference that efforts of his national security adviser, William P. Clark, to persuade the ABC network to delay its report on the Libyan situation had been unsuccessful.

White House officials were anticipating a question directly based on the ABC report saying that the Nimitz was off the coast of Libya.

Reagan was prepared to answer this question when he was instead asked a general question about the movement of the carrier, the sending of the AWACS planes to Egypt and the possibility of a Libyan attack.

"I don't believe there's been any naval movement of any kind," Reagan answered. "And we're well aware of Libya's attempts to destabilize its neighbors and other countries there in that part of the world. But the AWACS, this is not an unusual happening. We have conducted joint exercises and training exercises with the Egyptian air force . . . . We'll do more in the future. And these planes have been there for quite some time in Egypt, the AWACS planes, for this kind of an exercise and that's what they're going to conduct."

While one official said the president's comment about the AWACS was "less than artful," he insisted that the answer about the naval movement was technically correct because the question had been about the Libyan threat to its neighbors. The maneuvers of the Nimitz were described by several sources as related to another issue involving Libya, control of the Gulf of Sidra, whose waters are claimed by Libya but regarded as international by the United States.

Planes from the Nimitz flew over these waters although the carrier itself did not enter the Gulf of Sidra.

At the Pentagon, officials said they could see why Reagan considered the initial Nimitz deployment off the Gulf of Sidra unconnected to the emergency situation in Libya that led to the hurried dispatch of four AWACS planes from Tinker Air Force Base in Oklahoma to Egypt. The flights over the Gulf of Sidra were not related to attempts to stop the coup, Navy officials said.

Sources said the first two of these planes landed Monday in Egypt and were soon joined by two additional AWACS in an effort to provide round-the-clock surveillance of Libyan flights, particularly near the Sudanese border. At the same time the Nimitz was moving from its station off Beirut, where its warplanes were on call for the multinational force in Lebanon, to the central Mediterranean for flight drills.