Peruvian police and soldiers are "quietly" coordinating to free the hostages, Justice Minister Juan Jimenez told Canal N television, adding that "a democratic state like Peru does not negotiate with terrorist criminals."
"What the families of the kidnap victims must do is trust the authorities, because they are doing the right thing," he added.
The Swedish company Skanska and Peruvian firm Construcciones Modulares have called for the "speedy and safe release" of its employees who where kidnapped Monday in the Cuzco region of southeastern Peru.
On Thursday, President Ollanta Humala said the authorities were hoping to get the workers back to safety "in very short order," without making a ransom payment.
The guerillas are reported to have demanded $10 million in return for the hostages.
Some 1,500 troops have been deployed to cordon off the remote jungle region where the Shining Path rebel group are believed to be holding the hostages.
Of the abducted workers, 28 belong to Skanska and eight to Construcciones Modulares. The companies provide services to the international consortium that
operates the Camisea gas fields, the largest in Peru.
The government has established a state of emergency in the area for 60 days, with the suspension of certain individual rights, such as the inviolability of homes and the right of assembly.
Authorities sent their condolences to the family of police captain Nancy Flores, who died of a gunshot wound to the chest Thursday when she was taking part in the search for the 70 guerrillas who kidnapped the workers. The attack also wounded a police officer and a civilian.
The leftist Shining Path was largely dismantled when its leaders were captured in the mid-1990s, but not before a conflict that left some 70,000 people dead, according to Peru's Truth and Reconciliation Commission.
However, remnants of the guerrilla group still operate in remote regions of the country.