Guerrillas Step Up Attacks in Colombia : Violence: The rebel groups, excluded from the constitutional debate, are spreading terror in the capital. The death toll has reached 47.

BOGOTA, Colombia —  Leftist guerrillas excluded from this week’s first meetings to rewrite the Colombian constitution managed, nevertheless, to raise their bloody objection to the assembly.

Stepped-up actions by two guerrilla groups have resulted in the deaths of at least 47 people since the leftist attacks began Monday, hours before the opening of the constitutional assembly.

The two groups, the Revolutionary Armed Forces of Colombia (FARC) and the National Liberation Army (ELN), said in a joint communique that they had decided to escalate an offensive because the assembly “does not represent the interests of the people.”

Since Monday, rebels from both groups have carried out at least 56 attacks, burning buses, dynamiting oil and gas pipelines and ambushing military patrols.

Colombian officials said that the guerrillas are damaging the transportation and communications infrastructure in an effort to cut the capital of Bogota off from the rest of the country.

The administration of President Cesar Gaviria has steadfastly refused to allow the FARC and the ELN to participate in the constitutional debate unless they agree to lay down their arms under a government peace plan.

Three former rebel groups that took Gaviria up on his offer are represented in the assembly, which is charged with reforming Colombian democracy by rewriting the 104-year-old constitution. One of the groups, the April 19 Movement, known as M19, controls 19 of the 73 assembly seats.

Administration officials have refused to make major modifications in the peace plan despite the FARC’s and the ELN’s objection that it fails to address the country’s socioeconomic ills. But there were signs Wednesday that the government was shaken enough by the latest rebel violence to adopt a more flexible negotiating position.

Interior Minister Humberto de la Calle Lombana said that he is ready to meet personally with rebel leaders to seek a solution to the conflict.

The rebel offensive has darkened the cloud hanging over the constitutional debate, already threatened by drug traffickers.

In recent months, the Medellin cocaine cartel has kidnaped several journalists and other prominent Colombians in an effort to pressure the government into concessions. Gaviria later announced lenient judicial treatment for surrendering traffickers but administration officials insisted that there was no quid pro quo.

Two cartel bosses, Jorge Luis Ochoa and his brother, Fabio, have surrendered under the government plan, which includes a guarantee that they will not be extradited.

The cartel’s leader, Pablo Escobar, is still at large. He apparently has decided to wring from the assembly a constitutional clause prohibiting extradition in all cases. Suspected traffickers like Escobar prefer trial in Colombia, where they have been able to avoid prison by bribing and intimidating judges.

The cartel released one of its hostages late Tuesday in a gesture obviously aimed at influencing the constitutional debate. Several Colombian and foreign officials say that delegates are not only likely to discuss extradition but to kill it.

“Since there are only five or six assembly delegates that strongly oppose drug traffickers’ demands, I think the debate is likely to go Pablo Escobar’s way,” a Western diplomat said.

In his speech Tuesday to inaugurate the assembly, Gaviria exhorted delegates to withstand the attempts by both the rebels and the traffickers to coerce them.

“A popularly elected constituent body like this one . . . cannot be subject to intervention by any armed group,” the president said at a Bogota convention center, where the assembly will meet until June 4.

The FARC and ELN attacks have resulted in the deaths of some 250 guerrillas, government troops and civilians since the beginning of this year. Sabotage of oil pipelines and other infrastructure cost Colombia more than $100 million last month alone, according to a government estimate.

Guerrillas began the campaign in retaliation for the army’s seizure late last year of the FARC’s headquarters in southeastern Colombia.

Many Colombians are pessimistic that the government can make peace with the combined 10,000 combatants of the two guerrilla groups during the assembly’s deliberations. They say that the best that can be hoped for is a return to the occasional combat and sabotage that characterized the guerrilla conflict before January.

Others say that the unprecedented guerrilla violence has raised the stakes for both the government and the rebels.

“The country doesn’t want another uneasy truce,” said Rafael Serrano, a Conservative Party congressman. “It wants a radical and definitive solution to this problem.”