Melissa Reid (20) and co-accused Michaella McCollum, from County Tyrone, appeared at a closed hearing in Lima.
The women were caught with 11kg of cocaine – said to be worth £1.5m – at Lima airport in August, and said they were forced into carrying the drugs.
A court spokesman is reported to have said: “They will automatically have a sixth off the minimum jail sentence of eight years and will be sentenced to six years and eight months in prison.”
It is understood the pleas were made in exchange for a shorter sentence. They were due to be sentenced on Tuesday, October 1.
It has been reported that prosecutors in Peru are asking for another hearing to allow Ms Reid (right) and Ms McCollum to make a more complete confession.
Relatives of the former Lenzie Academy pupil say they have been “devastated” by Melissa’s ongoing ordeal, but buoyed by offers of help and messages of comfort.
Melissa’s aunt, Bernadette Gormal, has set up a Facebook page to allow people to voice their support.
She said: “We have a feeling of helplessness. You just want to do something.
“It’s helping the family. We’re devastated at what’s happened. Sometimes you really feel like you’re floundering. This isn’t a fictional drama for us – this is real life. We can’t switch off.”
* Have you got a story, picture or comment? E-mail [email protected]
Or you can log in below and have your say on the site...