Los Angeles  - The parents who triggered a massive alert after falsely claiming their six-year-old son was adrift in an experimental helium balloon are to admit charges related to the deception, their lawyer said Thursday.

The father, Richard Heene, will admit to attempting to influence a public servant, while the mother Mayumi Heene, will plead guilty to false reporting to authorities, lawyer David Lane said in a statement.

Lane said that the parents were pleading guilty to avoid the possibility of Mayumi being deported to Japan if found guilty of more serious charges.

The stipulated sentences for both are probation, his statement said, with the possibility of up to 60 days in jail for Mrs Heene and up to 90 days for Mr Heene.

"Upon reviewing the evidence, arguably, Mayumi could have possibly ended up being deported and Richard could have proceeded to trial and had a good chance at an acquittal," lawyer David Lane said.

"This, however, would have put the family at grave risk of seeing a loving, caring, compassionate wife and mother ripped from the family and deported. That was not an acceptable risk, thus these pleas."

The parents are to enter their pleas in a court hearing Friday in Larimer County, Colorado, close to where the drama unfolded in mid- October.

The parents had called authorities claiming that their son Falcon had accidentally taken off aboard the experimental craft, triggering a massive alert.

News helicopters followed the balloon, which at one point reached a height of over 2,500 metres, as aviation authorities struggled to come up with a plan to rescue the boy.

But when the balloon eventually floated back down to earth after an 80 kilometre flight it was found to be empty. The child emerged later to say that he was hiding in the attic, prompting immediate suspicions that the entire scenario had been a publicity stunt by the family which hoped to star in a reality TV series.(dpa)