Uganda can't seem to crush guerrilla leader Museveni

''Mao Tse-tung said if you get an egg and put it in an incubator, after a while it will hatch a chick. But if you put a stone in an incubator, nothing will happen even if you leave it there for 100 years.''

Yoweri Museveni, leader of antigovernment guerrillas in Uganda, was speaking in a camp concealed beneath the thorn trees and scrub of savanna country 100 miles north of Kampala, Uganda's capital.

He believes Western governments are wasting their time trying to persuade Ugandan President Milton Obote to improve his human rights record. Military repression is bound to continue, Mr. Museveni asserts, because the Obote government is losing popular support while the rebel movement is gaining.

Despite official United States acknowledgement that the Ugandan Army may have been involved in the massacres of thousands of civilians, the US assistant secretary of state for African affairs, Chester Crocker, has promised Uganda ''economic and humanitarian assistance.'' And the British government has renewed a training program for the Ugandan Army.

Mr. Museveni's National Resistance Army - some 6,000 guerrillas who have fought Obote's Army since disputed elections in 1980 - insist that the government should enter into peace talks proposed by Ugandan Roman Catholic Church leader Emmanual Cardinal Nsu-buga and opposition politicians. Otherwise, the rebels say, they will continue to try to force Obote out of power.

Fighting between the two groups has devastated much of the Buganda region north of Kampala. One million people once lived in the Luwero triangle region here, but now it is deserted and overgrown. Roads have returned to bush and mud houses have gaping holes where doors, shutters, and tin roofs have been stolen.

The fields that once provided matoke (green bananas) for Kampala and coffee and cotton for export are uncultivated. Fruit lies rotting beneath mango trees. This fertile farmland was once the richest part of Uganda.

There is also ample evidence of human starvation and killings. On a recent 10 -day trip with the rebel National Resistance Army (NRA), this writer was shown five dumping grounds where many bodies and bones were still scattered. I believe I saw approximately 2,000 bodies on the entire trip. Most of these bodies were close to former field camps of the government's Uganda National Liberation Army.

Peasants blamed the killings on the Army, and UNLA deserters talked of being ordered to go on ''general clearance'' missions to kill all peasants, young and old, in certain areas. In testimony last month before Congress, US Assistant Secretary of State for Human Rights Elliott Abrahms estimated that more than 100 ,000 persons have died here in recent years. But many regard that figure as too conservative.

''We estimate 300,000 people have died throughout Uganda since 1981,'' rebel leader Museveni says. ''Besides Buganda, people have died in Masaka, Mbarara, and West Nile although there has been no war there.''

The leader of the opposition Democratic Party, Paul Ssemogerere, thinks a more correct figure is 500,000 deaths since 1980.

The problem for President Obote is that support for the guerrillas among the Baganda and other southern tribes appears to be growing - despite the loss of life and land. The numbers of guerrillas are rapidly expanding. Conversations this writer had with dozens of residents of the region showed a great deal of antagonism toward the government. Many said they had relatives who had been killed, and many had moved off their land, into hiding, worrying that they too would be killed.

But if Obote curbs the excesses of the Army, he runs the risk of losing what appears to be a military parity with the guerrillas in the north.

The government and the Army are dominated by the northern Nilotic groups, especially the Acholi and Langi. The guerrillas and the opposition Democratic Party are largely drawn from the southern Bantu tribes, especially the Baganda and Banyankole.

Peasants north of Kampala say they back the guerrillas. This writer watched civilians exchange greetings readily with rebels and provide them information, water, and fruit. Civilians, who sell food to be rebels, say they want peace to cultivate their land. They argue the guerrillas are more likely to provide this than the government.

Many Ugandans here say they hold Obote responsible for growing tribal divisions. In the early 1960s, Obote, the country's first post-independence leader, broke off a political alliance with the Baganda and abolished the kabaka , their hereditary king. Obote then introduced a new Constitution giving the president sweeping executive powers. In 1969, he abolished parties other than his Uganda People's Congress (UPC).

Obote strengthened the Army by recruiting more Acholi and Langi. He appointed Idi Amin as Army commander, a man he thought was simple and pliable. That move backfired when Amin toppled Obote in 1971.

Previously unpublished Uganda Army figures show that Obote, now back in power and lacking support in some regions of the country, has built up the Army to 39, 516 men from a 1980 level of about 7,000. Of these, some 24,000 are militia, mainly recruited from the Acholi and Langi, the reports show.

Political parties are allowed to function, but the Democratic Party is perpetually harassed. Many of its members are fighting along with Museveni.

Museveni says he took to the bush and began armed resistance in l980, after Obote's followers allegedly rigged elections. He suggests that the proposed elections in 1985 will be a sham.

My estimate is that there are about 6,000 well-armed and well-disciplined rebels, up from 27 at the NRA's inception. Other exile sources say there are 7, 000 or 8,000 rebels. In most of its confrontations in this area, the NRA seems to come out on top in battles with the Army.

In February this year, the NRA Mobile Brigade captured large quantities of arms in the barracks-town of Masindi. Almost 2,500 soldiers were involved, its largest deployment to date. Museveni claimed this attack represented ''an advance in our level of organization'' and said he was planning future operations using two brigades.

Museveni has become an almost mythical figure in Uganda. His name is rarely mentioned by the government. Privately Ugandans will only refer to ''Sunday'' or ''two-plus-five,'' code for Mu-seven-i. Some peasants believe he cannot be hurt by bullets.

The rebel leader left Uganda the day after Idi Amin took seized power in 1971 and set up a resistance group. He became minister of defense in the coalition government that took over after the Tanzanian Army, along with many Uganda exiles, invaded Uganda in 1979, ousting Amin.

''We have the capacity to overthrow Obote. All we lack is supplies,'' Museveni claimed. In particular, the NRA lacks ammunition. He insisted: ''Our movement has no outside support. If we had, Obote would not be in power now.''

Museveni says the West is mistaken in assuming he wants to set up a Marxist state. ''I have never said Uganda should be run as a socialist or communist country.'' He wants a mixed economy based on production by the peasants and middle classes. He is not hostile to foreign interests and says: ''What I quarrel with are terms.''

Since the fall of Amin, the World Bank and the International Monetary Fund have backed an ambitious reconstruction program costing over $600 million. But the guerrilla war and general instability have now put the economic recovery in jeopardy.

The prospect of a full economic recovery in Uganda is still remote. Many say it can be achieved without a political solution. And this task is complicated by the fact that many Ugandans ultimately hold Obote responsible for the problems of the Amin era as well as his own.

Mr. Pike, who travels regularly in East Africa, is the first foreign journalist to have gone into Uganda's rebel territory since 1981.