TERRORISM / GAVIRIA’S OTHER CHALLENGE : Guerrilla Attacks Cut Oil Revenue : New Colombia president must find way to pacify rebel group

One of the toughest challenges faced by Colombia’s new president, Cesar Gaviria, is how to stop attacks by an armed group whose terrorist tactics have cost the country millions of dollars. The enemy in this case is not the Medellin cocaine cartel but a small band of leftist guerrillas, the National Liberation Army, or ELN.

The Marxist-Leninist group has caused serious damage to both the economy and environment through an unrelenting sabotage campaign against petroleum facilities. ELN leaders say they want the government to nationalize the oil industry.

Gaviria, in his efforts to pacify the country, must give priority to either coaxing or forcing the ELN’s estimated 2,000 armed members to lay down their weapons, government officials say.

The ELN has inflicted its greatest damage by dynamiting the country’s main oil pipeline, which runs about 500 miles from the rich Cano Limon oil field on the Venezuelan border to the Caribbean port of Covenas. Since 1986, 125 attacks have cost the industry nearly $500 million in lost production and repairs, the state oil company Ecopetrol said.

Future bombings are sure to be more costly. As a result of the Persian Gulf crisis, the world price of crude has risen, and Colombia, fighting a costly war with drug traffickers, needs the extra foreign exchange promised by the increase. The country exports about 200,000 barrels a day, almost all of it transported through the pipeline.

“Now, if the ELN dynamites it, the delay in exporting will mean much more in terms of lost income,” said Luis Soto, a Bogota petroleum consultant. “Making peace with the guerrillas is more important than ever.”

Many experts say the environment has suffered more than the oil industry at the hands of the ELN. Ecopetrol just completed a $1.4-million cleanup of what environmental officials call one of the worst messes ever left by an ELN attack. A May 12 attack on the pipeline caused 14,200 barrels of oil to spill into the country’s largest body of fresh water, the Zapatosa marsh, which feeds the Magdalena River in northeastern Colombia.

President Gaviria, who succeeded Virgilio Barco on Aug. 7, says he will try to stop the ELN violence by continuing his predecessor’s peace strategy, which stressed quick demobilization of guerrillas.

The one guerrilla group to lay down its arms under the plan, the April 19 Movement, or M-19, received several official promises in return. Among them was a guarantee that the government would work to reform the political system, long dominated by the Liberal and Conservative parties.

The M-19’s first presidential candidate, Antonio Navarro, finished third in the May 27 elections, and Gaviria, a member of the Liberal Party, appointed him health minister. The government is negotiating with three other small leftist guerrilla groups and has guaranteed their participation in a November assembly to reform the constitution.

ELN leaders dismiss the peace initiative as a farce. Some political scientists say the government will have to turn up military pressure on the guerrillas if it wants to persuade them to disarm.

But Gonzalo De Francisco, one of Gaviria’s peace advisers, says the administration’s main weapon will be state money invested in regions where the ELN operates. Barco’s Administration spent millions of dollars on public works projects in the states, including some ELN strongholds. De Francisco said the program would be expanded under Gaviria.

Spending of another kind played a role in the rise of the ELN. Colombian officials accuse the German firm that built the Cano Limon pipeline of paying the ELN a $6-million “oil tax” to let the work proceed in 1983. That payment whetted the guerrillas’ appetite for petroleum dollars and led to a string of kidnapings of foreign oil executives and other forms of extortion. The tactics transformed the ragtag band of rebels into a potent economic force in several rural regions.

Government officials and oil executives say the changes in the Communist world have removed the ELN’s ideological footing. But few here believe the ELN is ready to stop attacking the pipeline.