Dungannon woman Michaella McCollum could face six years and eight months in a Peru jail with no eligibility for parole even if they plead guilty.
But the prosecutor handling their case Juan Bautista Mendoza said that a further sentence reduction is possible if the pair co-operate as witnesses against co-conspirators.
Michaella McCollum, 20, from Dungannon, Co Tyrone, and Melissa Reid, 20, from Glasgow, were caught last month trying to board a flight to Spain with 24lb of cocaine in their luggage.
They have a court hearing on Tuesday where they are expected to be interrogated by a judge.
Each faces drug-trafficking charges and could be charged with up to 15 years in prison.
Ms Reid has already indicated she is likely to plead guilty.
Speaking on ITV’s Daybreak programme earlier this week, her father Billy Reid said she would probably make a plea bargain to “play the game” and get the case dealt with sooner — but said both he and his wife believe she was forced into the crime.
“Pleading guilty means that your case at least would come to court and you’d be given a sentence potentially within six months.
“If you continue down the not guilty route it can take two years to three years before your case even comes to court,” he said.
A lawyer for McCollum said after the women’s August 6 arrest at Lima’s international airport that they were coerced with threats of violence by a gang of up to 15 armed men, some of whom trailed them to Peru from Spain.
“I was simply repeating what she had told the police during the questioning,” Peter Madden told the Associated Press on Thursday.
He said he could not yet say whether McCollum, who has both Irish and British citizenship, would plead guilty or go to trial.
Mr Mendoza said that if both women plead guilty they could be sentenced to prison in less than a month’s time.
He said otherwise their trial could last six months.
The prosecutor said a new law enacted two weeks after the women’s arrest eliminated sentence reductions for good behaviour for people convicted of drug trafficking.
Previously, parole was possible after 32 months for drug couriers who pleaded guilty.
The women were arrested attempting to board a flight to Madrid with the cocaine hidden in packages of mayonnaise, said Mr Mendoza.
He said he did not believe that they were coerced into carrying the drugs, or in any way threatened, as they have claimed.