Morocco's recent completion of the sixth section of a defensive wall to keep a native rebel force out of the Western Sahara brings a new twist to the 12-year-old conflict: It threatens the neutrality of nearby Mauritania. The new section of the wall completes a more than 2,000-kilometer (1,242-mile) defensive system across the desert that has proved highly successful as an ``alarm system'' against attacks by the rebel movement, known as the Polisario Front.
The section also runs close to Mauritania's economically important iron-ore railway and reaches the Atlantic Ocean only 60 km (37 miles) north of Nouadhibou.
In addition to being the country's capital and its iron-ore export terminal, Nouadhibou is the center of the fishing industry that has recently become the country's main foreign export earner.
Col. Muawiya Ould Sidi Ahmad Taya, Mauritania's President, has described the situation on the northern border as ``serious'' and has sent envoys to alert various friendly countries. ``The massive and permanent presence of foreign troops so close to our vital centers is unacceptable,'' an official communiqu'e said.
A Western analyst said, ``The new wall means that in the future the Polisario will be obliged to launch attacks from Mauritanian territory. If Mauritania doesn't try to stop the Polisario, then Morocco might be tempted to pursue them across the wall.''
If the United States, France, Spain, and Saudi Arabia, some of the nations that take roles in backing Algeria and Morocco, react to the perceived threat to Mauritania, the war could be set to enter a more unpredictable phase.
Already, Algeria's President has visited Nouadhibou, Mauritania's northern port, in a show of solidarity with the Polisario, and French President Fran,cois Mitterrand raised the subject of possible Mauritanian involvement during an official visit to Morocco in April of this year.
In recent months, the Polisario has increased military operations, claiming in late April to have shot down a Moroccan F-5 fighter bomber and to have killed 137 Moroccan soldiers in the central eastern region of Western Sahara.
However, the Polisario's diversionary attacks failed to stop or even slow down construction of the new 550-km (342-mile) section of the Moroccan wall which was built in only two months.
A week after Algerian President Bendjedid Chadli visited Nouadhibou, Saudi Arabia, acting as mediator, arranged a meeting between Morocco's King Hassan and President Chadli at the Moroccan frontier town of Oujda.
Although the meeting, the first between the two leaders for more than three years, yielded no concrete results, it helped to restore a dialogue and reduce tension, observers say. There is hope that there will be more meetings in the near future. Analysts say there is currently much incentive to negotiate an end to the war. The economies of both Algeria and Morocco are suffering from the heavy expenses of the war combined with the drop in the price of oil.
The new wall of bulldozed sand and stones seals off the southern border of the western Sahara and is intended to prevent the Polisario from gaining access to the Atlantic Ocean, where the rebels have been attacking foreign fishing vessels and private yachts.
The fishing grounds off northwest Africa are among the richest in the world. Morocco has a bilateral fishing agreement with Spain, which is due to expire soon. Because Spain is now a member of the European Community, it is likely that the fishing agreement will be multilaterally renegotiated, observers say. The Polisario is pressing for Western Sahara's waters to be excluded from the agreement.
Surveillance of the desert wall is an immense task. Mauritania, though a large country, has only a small Army. It would therefore be practically impossible to prevent the highly mobile Polisario from crossing Mauritanian territory and launching raids across the wall, according to analysts.
If this scenario were to materialize, Mauritania could be dragged back into the war from which it withdrew in 1979 after a disastrous four years fighting alongside Morocco.
Mauritania broke relations with Morocco in 1981 after the latter was implicated in an abortive coup attempt. Mauritanians are traditionally suspicious of their powerful northern neighbor and what they see as Moroccan expansionist ambitions. They remember that in 1969 Morocco claimed the whole of Mauritania down to the Senegal River.
Mauritania officially recognized the Saharan Arab Democratic Republic, the governmental arm of the Polisario Front, in early 1984.
Since he seized power in December 1984, Mauritania's Colonel Taya has restored diplomatic relations with Morocco and pursued a policy of ``strict neutrality.'' This has enabled him to give full attention to promoting recovery of the nation's economy, which has been ravaged by drought off and on for 20 years and by its earlier involvement in the Western Sahara war.
Better rainfall the past two years has greatly improved harvests, but the country still imports nearly two-thirds of its food. Although the population is only 1.8 million, it is growing rapidly and food consumption outpaces production.
The country is set to receive its first World Bank ``structural adjustment'' loan, which will be accompanied by major reforms in food, banking, energy, and fisheries policies.
``The government is trying hard against heavy odds to save the country,'' an aid donor in sandblown Nouakchott said. ``Renewed fighting would be the last straw.''