The Kosovo Liberation Army has rejected a NATO plan to transform it into a small, peacetime civil defense group within Yugoslavia, leaving the rebel organization's future size and role undecided on the eve of a Sunday night NATO deadline for its demobilization.

Agim Ceku, the guerrilla group's military chief of staff, informed the commander of NATO forces in Kosovo, British Lt. Gen. Mike Jackson, of the group's objections to the NATO plan, NATO and KLA officials said. Ceku said that any new civil defense group must be larger and possess more armaments than NATO forces have been prepared to allow, and should also retain the word "army" in its title.

While NATO officials did not rule out an eventual agreement with the KLA, one said "there's still a lot to be worked out" and that no deal was imminent. He spoke several hours after KLA guerrillas paraded before an estimated 50,000 people and appeared at a raucous rally inside a football stadium here. The rally was organized with NATO's approval as a way of celebrating the ethnic Albanian force's wartime accomplishments.

In a speech, Ceku acknowledged the group will change after Sunday's deadline. But he reaffirmed that the new group's goal will be to defend the citizens of Kosovo, a role that NATO has said is reserved for the NATO-led force. Another KLA commander, Suleiman Sulemi, was even more blunt, insisting that "the KLA is now transforming into a modern army" because it is not finished securing Kosovo's independence from Serbia, the dominant republic of Yugoslavia.

Some NATO officials were surprised by the disagreements with the KLA, partly because they arose after what the officials had depicted as fruitful discussions with Ceku over the past three months. NATO remains adamantly opposed to the creation of "another army, in name or by any other measure," a spokesman for the Western alliance said.

KLA officials said several brigade commanders who helped fight a 14-month guerrilla war for independence against Yugoslav and Serbian security forces pressured Ceku into raising the objections and remained unwilling to accept a civilian future. They singled out Ramush Hajredinaj, who directed operations in western Kosovo near the city of Pec, and Sami Llushtaku, who ran operations in central Drenica, a few miles west of Pristina, the provincial capital.

Hajredinaj did not participate in the parade or rally because of what his aides described as his involvement this afternoon in a lengthy meeting with senior NATO officials. But a NATO spokesman, Lt. Col. Robin Clifford, said he was unaware of any such meeting. Llushtaku was present at the rally, but had previously told NATO officials the new group must be called an "army." If NATO refused, he reportedly said, the KLA would find its own solution.

Several KLA officials said that beyond picking a name, the KLA wants the right to staff a new organization with as many as 7,000 of its current members, most of whom would be allowed to carry weapons. NATO has said the new group should be allowed no more than 3,000 regular members and 2,000 reservists; it has also said no more than 200 members should be allowed to carry weapons at the same time.

According to NATO, the dispute has not undermined the KLA's compliance with the demilitarization deadline, and Jackson is prepared to announce Sunday afternoon that all requirements have been met. Several officials noted that, in fact, the KLA has turned in more weapons in the past three months than it initially declared.

In western Kosovo, for example, the group turned in 2,500 rifles, 215 machine guns, 150 mortars, 1,000 mines, 4.5 million rounds of ammunition, 100 antitank weapons and thousands of hand grenades, said Italian army officers in NATO's headquarters in Pec. The total is more than double what the KLA had promised in July--a number that some NATO officials had said was too low.

"We will be the last ones to pretend . . . that Kosovo is now weapons-free," a NATO spokesman said Friday. But "for the moment, we have been . . . satisfied with" the KLA's compliance.

The KLA's resistance to NATO's plan is not cause for alarm, a U.S. diplomat said. "We always expected that some of their fighters would reject it and possibly go into crime or the hills," he said. "Our objective has been to try to use the majority to keep the others under control."

He said that Washington is prepared to contribute $15 million toward an estimated $40 million to $70 million for the new civil defense group, with NATO allies supplying the rest.

At today's rally, Hashim Thaqi, a former KLA guerrilla who was selected as interim prime minister by Kosovo's political leaders last spring, was the only official who expressed support for NATO's concept of a civilian corps. With Serbian forces ousted from Kosovo, he told the assembled KLA members, "you will have other duties" besides fighting. He also reminded them that the United Nations and NATO have guaranteed they will protect Kosovo's borders.

Dozens of civilians in the crowd waved red and black Albanian flags, and some held up signs saying "We are the KLA," while schoolchildren sang a popular tune that includes a pledge to "die for Kosova" and its freedom.