CHAMBINGA, ANGOLA -- -- By all appearances, the inhospitable savannah around this sun-scorched hamlet is deserted, except for the occasional wart hog rooting in the deep sand or a pair of antelopes nervously sniffing for predators.

Suddenly, a clump of thorny foliage moves, revealing four camouflaged guerrillas manning an antitank gun pointed menacingly to the west. Nearby, light machine-gun emplacements protect a wire-guided TOW antitank missile position, and the eye begins to discern, through the concealing foliage, bazookas, recoilless rifles and hundreds of combat-ready soldiers.

The stillness is abruptly shattered as nearby artillery batteries unleash salvos of mortar shells and Katyusha rockets, answered in minutes by enemy mortar fire that falls far wide of its target.

The classic defensive deployment is not a welcome position for the anticommunist rebels of Jonas Savimbi's National Union for the Total Independence of Angola (UNITA). As UNITA braces for what Savimbi says will be a "life or death" offensive by the Cuban-backed forces of the ruling Marxist Popular Liberation Movement of Angola (MPLA), the rebels have been forced to abandon their guerrilla tactics and adopt the uncomfortable posture of conventional warfare.

While touring his front-line positions barely two miles from the forwardmost government deployment in southeastern Angola, UNITA's vice chief of staff, Gen. Ben Ben, said, "This is very conventional warfare. They have pushed us into it. With the figures, we can't make a conventional war, but here I think we can deal with it."

Ben was one of 12 supporters Savimbi took to China in 1965, before Angola's independence, to study the principles of guerrilla warfare under the tutelage of then-prime minister Chou En-lai.

Savimbi, speaking at a command post at Mavinga, a rugged 10-hour drive by truck southeast from here through the trackless bush, seemed equally disconcerted by the stand-up confrontation his guerrillas face 18 miles east of the government-held city of Cuito Cuanavale.

"We don't want to fight them on their terms," Savimbi said in an interview. "If we fight on their terms, which is conventional, then we could lose. In the whole country, it is a guerrilla war. We like to go behind them in the flanks. Where they don't expect us, we are there. Where they do expect us, we are not there." He added, "We don't like this kind of war in Chambinga . . . . We like guerrilla war, to attack when we are ready to attack and not to attack when we are not ready."

The UNITA forces, backed by the United States and South Africa, are digging in for the main thrust of a dry season offensive that their military intelligence analysts said could begin this week.

UNITA expects the MPLA to push armored and infantry columns east toward Mavinga, as it did in a 1985 winter offensive. Not only is Mavinga strategically important as a gateway to the rebels' bush headquarters at Jamba, but it produces virtually all of the food for the UNITA-controlled southeastern corner of the country, called "Free Angola" by the guerrillas.

In 1977, after losing a struggle with the MPLA for control of Angola, Savimbi led his anticommunist followers on a trek to this region, where they established their enclave in a former game preserve.

Before South African forces intervened in 1985 with massive air support, MPLA troops drove east beyond the Lomo River, nearly reaching Mavinga and delivering a telling blow to the rebels' morale and prestige. But they failed to capture Mavinga before having to fall back to Cuito Cuanavale.

The battle at Chambinga -- should it materialize -- could be critical in determining whether the government and UNITA will ever sit down at a negotiating table in an effort to resolve the 10-year-old civil war.

Front-line UNITA commanders said they expected three major MPLA thrusts: one from Cuito Cuanavale; another from Munhango, on the Benguela railway line at the northern edge of UNITA-controlled territory, and the third starting at Lucusse to the east.

In Luanda, the capital, government officials have insisted that they have no intention of launching a major offensive this winter, despite estimates by the United States that the Soviet Union has sent $1 billion worth of arms to Angola in the past year in preparation for a massive attack against UNITA.

Following a visit to Luanda last month in which he unsuccessfully pressed for peace negotiations, U.S. Assistant Secretary of State Chester A. Crocker said a major government offensive was imminent.

Savimbi said he is certain the offensive will begin in earnest before the onset of rain in the next two months, after which the government forces would be unable to move armor easily through deep sand and across swollen rivers.

He said the denials in Luanda of any planned offensive are calculated to save face should the initial thrust against UNITA's defensive line here fail. In fact, the rebel leader said, the offensive in effect began on July 10 when government forces moved from their positions eight miles east of Cuito Cuanavale and halted on high ground at Chambinga to reorganize their infantry and armored brigades.

UNITA commanders at the front and intelligence analysts in Jamba estimated that the MPLA is in the process of massing 12 brigades at the front, totaling of 12,000 to 15,000 men, excluding a backup Cuban regiment that is protecting Cuito Cuanavale and Angolan logistical brigades that could be pressed into combat.

Savimbi said all MPLA brigade commanders at the front were summoned to Cuito Cuanavale on July 29 for two days of meetings with the high command and Soviet and Cuban advisers. He also said that 200 Soviet-built tanks had moved from Menongue to Cuito Cuanavale, and that UNITA had listened to Cuban tank commanders talking by radio.

Officials in Luanda maintained that the estimated 37,000 Cubans in Angola have not been used in combat for several years and are deployed primarily to defend strategic cities and provide technical assistance. U.S. officials estimated the Soviet presence at about 1,000.

Angolan Army regional commanders, in interviews last month in Lubango, capital of adjacent Huila Province, scoffed at reports that such a massive build-up was under way, and said they would not risk the South African intervention that would inevitably follow a major offensive toward Mavinga and the Jamba enclave.

Savimbi's rebel commanders declined to pinpoint their front-line strength, but their outspoken confidence, and the evidence of their deployment along a three-mile-long defensive line here, suggests that a sizable proportion of UNITA's 28,000 regular troops would be available to try to stem an MPLA advance.

"We learned in 1985 not to put all our forces in one place. So we still have forces south and west of Cuito Cuanavale. Always when they push ahead, they leave their rear vulnerable, so we are leaving some of our forces behind them to harass their supply lines," Gen. Ben said.

UNITA's chief of military intelligence, Brig. Perigrino Wambu, said in an interview, "The major vulnerability of the MPLA is their logistics. With our guerrilla actions behind their lines, we will force the enemy to pull out of the conventional front to protect their supply lines . . . . By cutting off their logistics, we are cutting their throats."

UNITA's tactic on the conventional front line, according to Gen. Ben, is to confront the government thrust with rebel infantry, which would fall back and lure the MPLA tanks and armored vehicles toward the UNITA antitank positions. The effectiveness of the first armored assault through what he called the "logical route to Jamba" could be decisive, Ben said.

Savimbi also emphasized the potential decisiveness of the expected offensive.

"It is a question of life or death for UNITA," he said. "On their side, it is a question of lose and start to negotiate. They will have to talk with us if they fail. On our side, it is lose and disappear."

Air strikes by Cuban- and Angolan-piloted MiG23 fighter-bombers pose a particular danger to the UNITA forces. The point was illustrated last week during a trip from Mavinga to the front when a truck loaded with 25 UNITA commandos and a foreign journalist was forced to race for the cover of a stand of scrub trees as the jets approached from the northwest.

On the return trip, the convoy took a different route through heavily forested terrain.

The arrival of U.S.-supplied Stinger antiaircraft missiles as part of $15 million in covert aid provided by Washington last year has helped somewhat to blunt the aerial threat. Savimbi, while declining to discuss the Stingers, said the UNITA-controlled area between Cuito Cuanavale and Mavinga is "saturated" with antiaircraft devices, adding, "If they fly low, we will try our best to shoot them down with conventional weapons. If they fly high, we have some instruments."

In the longer view, Savimbi said, UNITA's strategy remains one of trying to cripple Angola's economy through hit-and-run operations.