Eight months of secret U.S. efforts to win Egyptian approval for a U.S.-Egyptian military operation designed to overthrow Libyan leader Muammar Qaddafi appear to have foundered following public disclosure and rejection of the plan by Cairo, informed sources said yesterday.

Still, there were contradictory reports yesterday on whether the plan had been abandoned by the United States. Officials were quoted this week in Cairo as saying that the Egyptian government had rejected three U.S. overtures in recent months for a joint attack on Libya. U.S. sources, however, said that secret discussions in Cairo in February were productive and the joint planning was continuing.

One option of the plan called for U.S. military air operations in coordination with Egypt, which would attack across the 600-mile Libyan-Egyptian border. U.S. support was to include extensive bombing in what one source said would have been the most ambitious and aggressive foreign policy decision in the Reagan administration.

President Reagan authorized the planning and in the last eight months sent two high-level emissaries to Egypt for secret military planning, according to informed sources. One emissary, Vice Adm. John M. Poindexter, now Reagan's national security affairs adviser, headed a team of military planners that visited Cairo late last summer around Labor Day; a senior Pentagon general assigned to the Joint Chiefs of Staff continued the efforts this February in meetings that one source said "went very well."

Reagan never gave final approval to carry out the military plan even if Cairo had assented and sources disagreed yesterday about how close it came to realization. "It was really a plan for a surprise attack on Libya in conjunction with Egypt, nothing less," one source said.

The Defense Department last year also slowed its planning when strategists concluded that as many as six divisions, or 90,000 men, would have to be used if direct U.S. military involvement was required.

"The whole attitude of the Pentagon study was," said one source, " 'Do we want a war with Libya?' " Libya's armed forces include 73,000 regular troops and 535 combat aircraft.

The joint U.S.-Egyptian military discussions were one of the most closely held undertakings in the Reagan White House, sources said. "A small group of mostly senior advisers took the war-making power unto themselves," one source critical of the planning said recently. "They had insufficient understanding of the Middle East . . . . It could have been a disaster."

Even while disagreeing over details of the plan and its current status, a number of sources agreed that it was not to be executed until there was a clear-cut military or terrorist provocation by Libya and Qaddafi, its erratic leader.

One part of the U.S. plan called for Egypt to attack Libya on the ground, occupying perhaps half the country. Then, at Egyptian request, the United States would step in to assist. Another scenario suggested that once in control of half of Libya, Egypt would have sufficient leverage to force Qaddafi out of power.

In another alternative, U.S. bombers and tactical fighters would strike major Libyan military installations before the Egyptian attack or in concert with Egypt's attack.

Despite Egyptian hostility toward Qaddafi, the sources said, some U.S. strategists believed that Arab solidarity likely would have prevailed, preventing Egypt's participation with the United States in any large-scale attack against an Arab neighbor unless Libya attacked first.

Some administration officials have described the plan as "precautionary" and a "contingency." Several sources have said that the U.S. Navy exercise last week in Libya's Gulf of Sidra -- code-named "Operation Prairie Fire" -- may have satisfied the administration's goal of sending a message of U.S. resolve to Qaddafi. Three U.S. aircraft carrier groups retaliated against a Libyan missile attack by sinking at least two Libyan patrol boats and bombing a missile radar site.

In December and January when The Washington Post learned of some of the secret planning with the Egyptians, certain details about ongoing military plans were omitted from articles after a request from senior administration officials. On Dec. 21, The Post reported that a high-level emissary for anti-Libyan military contingency planning had been sent to the Middle East. In a Jan. 24 article, Egypt was first identified as a key participant in the secret planning. Poindexter was not identified as one of the emissaries to Cairo until an article last Wednesday in The Post in the wake of the Gulf of Sidra action.

Poindexter's role as the planning emissary to Cairo was a closely held secret and apparently triggered a response in Egypt.

Ibrahim Nafeh, editor in chief of the semiofficial Al-Ahram and a man close to Egyptian President Hosni Mubarak, wrote on Monday that "the United States has attempted more than once to join in an action with Egypt against Libya." He cited three such attempts and said that Egypt had rejected the proposal each time.

The Washington Times yesterday said that administration sources confirmed these reported rejections.

Well-placed administration sources, however, said the Egyptian reaction was not outright rejection and that during the February meetings in Cairo a senior Defense Department planner reported positive results. The White House had no comment yesterday.

There is apparent division in the Egyptian government about the U.S. plan, and one source said that Egyptian Defense Minister Abdul-Halim Abu Ghazala, a defense attache in Washington during the mid-1970s, was more inclined to at least listen to U.S. plans.

U.S. relations with Egypt were strained last October after the hijacking of the Italian cruise ship Achille Lauro, when U.S. jets intercepted an Egyptian airliner carrying the four hijackers. An article the next month in The Washington Post detailing a covert CIA plan to attempt to undermine the Qaddafi regime -- which has been only a portion of the administration's anti-Qaddafi plans -- also increased Egyptian fears that any joint undertaking against Qaddafi with the United States would become public.

Abu Ghazala was apparently upset about the CIA disclosure, according to an intelligence report, and was told by the U.S. embassy in Cairo that the story would not arouse much controversy because nearly everyone in the United States favored unseating Qaddafi.

The seriousness with which the anti-Libyan planning was undertaken by the White House is illustrated by one written analysis about probable Soviet reaction to a military strike against Libya prior to the November summit meeting. The analysis concluded that the Soviets would keep their distance, and any U.S.-Egyptian move would not hurt the summit.

As details of the plan were disclosed to Pentagon and intelligence analysts over the last eight months, serious objections began to surface. No one in the White House had fully grasped the extent to which Qaddafi, who has ruled since 1969, has a hold on the Libyan population of 3 million people, according to one informed source. Through a series of so-called revolutionary committees, Qaddafi has organized and armed the population, in some instances down to individual blocks in the Libyan capital of Tripoli. These people's committees are fiercely loyal to Qaddafi, according to some U.S. analysts.

The Pentagon, according to sources, was also concerned that the planning did not fully deal with the task of launching and coordinating such a military operation across the Atlantic.

"This wasn't Grenada," one source said, "though there were frequent references to it in the discussions.