Although repeatedly dismissed as little more than a nuisance by the Angolan government in Luanda, guerrilla leader Jonas Savimbi remains confident and optimistic that he will succeed some day in overthrowing it.

At Savimbi's personal invitation recently, eight reporters were flown to his hideout in southern Angola from a neighboring African country so he could prove his continuing viability.

"I want to show you that UNITA is viable and controls almost half of Angola [which is almost twice the size of Texas] and convince you that we are going to reach Luanda one of these days and take over the country," Savimbi said.

The journalists in their 18-day trip with Savimbi's UNITA [National Union for the Total Independence of Angola] guerrilla forces in southern Angola, saw his fighters to be disciplined and dedicated but without the support that would seem necessary to defeat the government forces.

Savimbi, however, remains optimistic. An ebullient fellow, he is, hard to pin down on his claims. A sketch he made of the areas he says are UNITA controlled or dominated seemed to cover only about a third of the country, and his absolute control seems to be only in the southeast province of Cuango-Cubango.

It is a desolate region, usually shunned even by tribesmen, but with enough water and grass to support wildlife such as the sable antelope, foxes, buffalo and storks.

The trackless scrub forests of Cuango-Cubango serve UNITA well as a rear base area. Among the well-hidden clusters of huts that make up UNITA's camps, recurits train and then begin the long trek north to harass government forces in central Angola.

The Benguela railway, built to carry the copper ore of neighboring Zaire and Zambia to the Port of Benguela, is a favorite target for the guerrillas, and Savimbi claims that they have kept the railroad inoperative by blowing up bridges and other sabotage since 1976. (The government's manager of the line says, however, that it has been reopened and is operating normally.)

Savimbi also claims that his troops in central Angola are so aggressive that the government's forces and their Cuban allies are unable to venture out of their garrisons in the towns without being ambushed.

Besides attempting to embarrass and weaken the Soviet-backed regime with his creeping offensive into central areas still controlled by the government, Savimbi has intensified his effort to take and hold down along the Angola border with Namibia (Southwest Africa) in the south.

He has a political motive for doing so. The current U.N. proposal for bringing about independence and representative rule in Namibia, which is administered by South Africa, includes the establishment of a demilitarized zone along the 1,500-mile Angolan-Namibian frontier as a way of preventing infiltration of insurgents into Namibia.

Savimbi says he is all in favor of this -- as long as he is consulted about his status in the zone. This is the guerrilla chief's way of trying to obtain a degree of recognition from the United Nations, which until now has not acknowledged his presence.

Although Savimbi talks in mildly revolutionary terms, mentioning socialism and nonalignment as policies he would adopt should he come to power, his determination to drive the Soviets out of Angola might be expected to bring him meaningful support from the noncommunist world. But there is no evidence that it does. CAPTION: Picture, Jonas Savimbi, in uniform of a three-star general, rests in his conference hut. Copyright (c) Jason Laure