In the Western Sahara near the Moroccan-controlled town of Smara there is a large sign erected by Saharan guerillas who want to throw the Morroccans out. The sign marks the entrance to a guerilla base camp, and in carefully hand-scripted Arabic it commands, "Do Not Enter."

Four hundred miles away, 38-year-old Lalti Smael Bardi eased her Soviet-make Kalishnikov assault rifle off her shoulder and knelt in the sand. She breathed lightly, despite the fact that for the last two hours she had been jogging, marching, firing her gun and throwing herself prone in the searing mid-day heat.

She had not yet participated in an offensive military operation, she explained, but like the other women in her unit, she had done defensive duty.

"When our training is completed we will fight alongside the other guerillas," she said, adding that her son was also in the army. "If necessary his children will fight one day, too. But how ever long it takes we will win."

That attitude of defiant confidence is characteristic of the Polisario Front independence movement that is opposing a takeover of this former Spanish by Morocco and mauritnia, who divided the territory by agreement with Spain 18 months ago.

In the four years since its formation, Polisario has grown from a youthful band of desert fighters attacking Spanish outposts with ancientist organization that has nudged northwest Africa to the brink of regional war.

Its spectacular hit-and-run "raids against heavily fortified targets hundred of miles inside Morocco and Mauritania have prompted political leaders in both those countries to consider attacking neighboring Algeria, which supplies the guerillas arms.

The tenacity of the Saharans has confounded observes who believed the Moroccans would easily crush the flegling independence movement. With an estimated 10,000 guerillas, the Front has pinned down 35,000 Moroccan soldiers and forced a dramatic increase in Mauritania's army from 1,200 men to today's level to 12,000. Polisario has given up its, camels for Land-Rovers and jeeps and traded its musket for SAM-7 missiles capable of downing Morocco's most sophisticated jets.

The result is an escalting conflict with the guerillas apparently on the offensive.

During a week's trip with Polisario (an acronym for Popular front for the Liberation of Saguia el Hamra and Rio de Oro) I had an opportunity to test the guriellas' claim that they roam freely over much of the territory's 103,000 square miles, confining the Moroccan and Mauritanian troops to isolated villages that must be supplied by air or arms convoy.

According to the Saharan, Morocco holds only 11 towns and Mauritania clings to another four with Moroccan help.

That kind of statement is dismissed as sheer bravado by the Moroccans, who until-last month refused to recognize that a war existed. Morocco's claim to control this desert are viewed by most U.S. diplomats as being more reliable than the assertions of the Polisario who talk of liberated areas" and improbably high casualty rates among Moroccan and Mauritanian forces.

"From what we can tell, Polisario penerates the frontiers only occasionally," said U.S. official. "Morvco has put 5,000 crack troops in special counter-insurgency units. They appears to have pretty well cleaned the guerillas out."

But a trip with the Saharan Army gives the impression that Polisario has a far stronger internal base than the diplomats have recognized. In a journey of 700 miles that took me and a travelling drive of the capital, El Aziun, and included a sidetrip into northern Mauritania, we were never far away from a permanent guerilla camp, each housing hundreds of combatants as well as medical facilities and guerillas for captives.

Despite the guerrillas attempts to entice the Moroccans out for a skimmish when we circled the fortified town of Smara, the only sign of the Moroccon presence was an occasional destroyed tank or vehicle and the remnants of bomb casings.

By contrast, the Saharans are mounting several raids a day in widely scattered of the territory aid in recent months have aimed at larger, better-protected targets. They have apparently overcome traditional ethnic divisions to mold a unified fighting force including both black coastal people and the Arab Berber nomads of the desert interior.

Ours was a typical Saharan raiding party - a group of 20 to 30 soldiers armed with Kalashnikov rifles and French 36 mm. Mausers traveling in bullet-riddled vehicles captured from the Spanish or the Moroccans. Extra fuel tanks were unnecessary because supplies were stashed all along the route, but several spare tires for the frequent blowouts proved essential.

The trip began in the harsh Iguidi Deserr of southern Algeria, where between 65,000 and 100,000 Saharan refigees - a majority of the territory's population - live in 22 ill-equipped tent cities near the town of Tindouf. They subsist on donations from international relief agencies, supplemented by Algerian governmnet aid at the rate of $50,000 a day.

Although technically on Agerian territory, the camps are run by Polisario, which declared Western sahara a republic and itself a governmnet on Feb. 27, 1976 - the date Sapnish rule formally ended. Administratively, Saharan guerillas control begins at the last Alferian checkpoint a few miles west of Tindouf. There, a passports are examined and early and exit forms filled in. If a trip inside Western Sahara is on the traveler's agenda, a letter is required absolving tthe Algerian governmnet of all responsibility in case of dealth or injury.

We left Algerian at dawn, in a Toyota Land Cruiser smeared with brown grease to prevent its chrome and glass from glinting in the sun and alerting Moroccan reconnaissance planes. For the same reason, three escorting Land Rovers had no windshields or mirrors.

THe precautions were of no apparent usefulness expect during a Polisario bombardment of Smara, which we watched from a rocky outcrop three miles away. At other times the Saharans traveled on the desert version of major highways - well-drained routes in the sand that could be spotted only from thousands of feet in the air. For a day and a half our progress was further marked by clouds of dust raised by an accompanying supply convoy. Its four petroleum tankers and six heavy transport trucks often floundered in deep sand, seemingly a perfect target for Moroccan bombers,

=We're not afraid of Morrocco's airplanes," said Mohamed Lamine, the military commander of the central region, whose base camp sports the "No Entry" sign. "If they fly low enough to bomb us we shot tham down."

From a short distance away the camps looked like the other clusters of thorn trees that speckled the desert. Only when literally under their branches was it possible to see the bright geometrics of rug flooring, the rifles slung from branches, and the adobe walls that hid groups of soldiers sitting cross-legged around smoldering braziers.

When a low-flying reconnaissance plane came directly over a camp one evening, none of the guerrillas appeared to notice. Only the obvious anxiety of their guests persuaded them to momentatily dim the head-lamps of three nearby Land-Rovers in whose circle of light damaged tires were being repaired.

Later, at an open-air camp between Smara and Amgala the saharans built a brush fire to ward off the chilly night temperatures, 80 degrees cooler than the afternoon high nearly 140. Over amela of fresh geme, dried camel meat, and crusty bread baked in the sand, the guerrillas told strikes of the war.

"We used to build fires and then hide in the rocks," said Mohamed Lanive. "When the Moroccans came we would ambush them. Now, when they see a fire, they go the other way."

"The life of a soldier in the People's Army is a joyous one," said Mohamed Ferrati, who worked as a phosphate miner at Bou Craa until joining the querrillas. He added, however, that to fight for independence erequires sacrifices. "When the Morrocans bombed the Amgala oasis my 2-year-old son, my only child, was killed," he said.

The guerrillas claim that , like Amgala, the village of Tifariti was deserted under heavy bombardment early lasy year. Morocco denies it. According to Moroccoa stastistics, 1,813 registered voters cast ballots in municipal elections there a month ago. Moroccon officials say the "Tifariti" shown to journalists was built by Saharan nomads to fool the international press.

If so, the deception is an elaborate one. The town is a hollow shell, its white-washed domes caved in upon tile floors. Only Polisario look-outs walk the rubble-strewn streets, past fallen unitility poles swinging crazfly from criss-crossed wires. On a hill approaching the village, a burned out tank sits like an aged sentinel, keeping watch over an empty grain silo. Nearby a propellor and a tall fin sandwich the ruins of an airplane.

Farther south, about 35 miles from the Mauritanians garrison at Bir Moghrein, the relics of war were more gruesome. The decomposing remains of four bodies lay among the twisted metal shards of a Mauritanian aircraft, their bleached bones still poked into decaying amy boots.

While we examined the wreckage, a plane the guerrillas identified as an American-made F-5 passed high above us, and we froze lest its electronic equipment detect our vehicles.

"Don't you wish your governmnet hadn't sold Morocco all those bombers?" joked our driver a few moments later, as we raced toward the safety of surrounding hills.

It was a points the guerrillas returned to often. "Without the aid of powerful Western interests Morocco could not continue this war," said military commander Mohamed lamine, referring to France and the IUnited States.

American officials are publicly neutral. They are both traditional ties with Morocco, which hosts naval installations and CIA communitions facilities at Kenitra, Sidi Yahya, and Sidf Bouknaded, and growing economic links with Algeria, whose governmnet-owed natural gas company has signed contracts promising most of the next decade's production to U.S. companies.

Privately, U.S. diplomats concede that thry would like to see a Polisario governmnet in Western Sahara with close ties to Algeria as well as to Libya's Col. Muammar Qaddafi, who is also thought to be supplying the guerillas with arms. They worry that a Polisario victory would tip North Africa's balance of power toward Soviet interests, at the expense of staunchy anti-Communist King Has-

"If (Algerian President Houari) San II.

Boumediene gets away with this, where will he stop?" asked a highly placed official.

In closed congressional hearings at the time of Spanish withdrawal from the Sahara State Department and Pentagon officials testified that they were approving a $120 million sale of 24 F-5E jet fighters to Morocco because of a need to counterbalance Algeria's superior air power. Military aid credits to Morocco have risen to $31 million from the pre war level of $3.6 million, and the Carter administration has requested $45 illion for fiscal 1978.

The belief that Polisario advances might alter the political face of north west Africa is shared by the Saharan guerrillas. A front political statement says, "The liberations of the Sahara is only a beginning. We invite all the patriotic forces of Morocco and Mauritania to join us in putting an end to the (their) regimes.

American officials are hopeful that a negotiated settlement between Algeria and Morocco is possible, although a Saudi Arabian attempt to mediate the dispute failed last fall. They believe an impoverished Mauritania would fall into line with any agreement made by Morocco, and that Polisario would cease to be a factor without Algerian backing.

Polisario leaders here scoff at such suggestions, saying Algerian prestige is on the line. "Algerian has supported Saharan self-determination in both the United Nations and the Organization of African Unity," said Mahmoud Abdel Fettah.

The guerrillas admit that a settlement, if it happened, would pose immense difficulties for them, but they deny that it would end thw way.

"We fought the Spanish, then the French, and then the Spanish again; now it is Morocco and Mauritania," said Mohamed Ferrati. "We know our desert very well, and we are in no hurry. We will flight as long as it takes."