RAMA, Nicaragua (AP) _ Despite repeated threats to cut the Rama Road, anti-Sandinista rebels have not been able to slow traffic on Nicaragua's most strategic highway.

Large convoys of military trucks regularly rumble over the 166 miles of broken, potholed road, unmenaced by Contra guerrillas who roam the nearby hills and jungles.

Destruction of any one of several major bridges along the road would halt traffic for days, if not weeks, according to military experts in Central America. Such a disruption would add fresh woes to an already shattered Nicaraguan economy that relies on the road for shipments of scarce and badly needed goods and tons of military supplies.

Most of the experts attribute the Contras' ineffectiveness to poor leadership.

The Rama Road is part of the highway and water route that links the capital of Managua, near Nicaragua's Pacific coast, with the town of Bluefields and the important, nearby port of El Bluff on the Atlantic.

In the past two years, the route has become strategically important to the Sandinista government in Managua - and to the rebels who oppose it. Over it travels most of the military and other supplies provided to Nicaragua by Cuba, the Soviet Union and other Eastern European countries.

Starting at Managua, the two-lane, blacktopped road loops toward the southeast and the town of Juigalpa, wending its way through low, almost barren mountain valleys unsuited to guerrilla operations.

From Juigalpa, the road takes a more direct southeasterly route, climbing the mountainous spine of Nicaragua and then dropping down into low, jungled savannahs before ending at Rama, almost three-fourths of the way across the country.

From there, people and cargo move in boats and barges to and from the port at El Bluff, which has been greatly improved in the past few years. The advantage of El Bluff is that it eliminates the need to ship goods through the Panama Canal to Nicaragua's Pacific port of Corinto, cutting both distance from European ports and the possibility of detection of sensitive cargos.

The Rama Road is most vulnerable between Juigalpa and Rama, a stretch where it is guarded most heavily. The Sandinistas have sharply increased security recently, patrolling the route with regular troops, special counterinsurgency forces, elite units of the Interior Ministry and even reservists.

Nonetheless, security seems somewhat lackadaisical.

Another reporter and I drove to Rama recently without proper government clearance and, although we were stopped at half a dozen roadblocks, nobody asked for our credentials.

It was not until we reached Rama, a grubby, ramshackle town of about 5,000 people, that we were challenged.

A state security policeman, who presumably had seen our names on the hotel register, demanded to see our identification and, when we were unable to produce special permits to visit the area, told us we would have to return to Managua the next morning.

We readily agreed, since we had planned to leave by then in any case. On our return, we passed the same roadblocks; again, we were challenged by soldiers who generally chatted with us freely.

In Rama, Lt. Roger Urbina, information officer of the Nicaraguan army's 525th Battalion, admitted that an estimated 1,500 to 2,000 rebels are operating north of the Rama Road, in Zelaya, Chontales and Boaca provinces.

He referred to the Jorge Salazar Brigade, a Contra unit which infiltrated central Nicaragua last summer and has been operating in that area. It is part of the U.S.-backed Nicaraguan Democratic Force, known by its Spanish initials as the FDN and the largest of several rebel groups operating in this country.

''They move in groups of 100 to 150 men, attacking (farm) co-ops, health centers and conducting kidnappings,'' said Urbina. ''But they do not move on the road and so far they have not attacked any convoys.''

''It is possible they will try,'' Urbina added, ''because it is their plan to try to cut the road.''

That plan was announced last fall by Enrique Bermudez, the military head of the FDN, which operates primarily in northern Nicaragua from bases inside Honduras.

Months earlier, Eden Pastora, commander of another rebel army best known by its Spanish initials as ARDE, also set as his primary goal the cutting of the Rama Road.

But Pastora's ARDE troops were routed from their camps along Nicaragua's border with Costa Rica late last year in a major Sandinista offensive and have been unable to resume operations on any significant scale.

The Contras' biggest success along the road came last Dec. 20 when they surprised an encampment of about 50 reservists near Presillitas, about 14 miles west of Rama.

''They were reserve troops from Managua,'' Urbina said. ''It was a Sunday and they had had a party and some of them were sleeping'' when the attack came at about sundown.

The lieutenant said 33 reservists and five civilians were killed in the guerrilla raid.

Urbina said the guerrillas also made three attempts to blow up a bridge at Cara de Mono, 20 miles west of Rama, in November and early December, but were easily driven away, in one case with a loss of eight dead and eight wounded.

The Sandinistas have strung barbed-wire barricades around all of the vital bridges along the Rama Road and planted mines beneath the spans to discourage rebel sappers.