She said that the assault took place in Las Vegas hotel.
The ongoing scandal is not the reason for his absence, however, with Portuguese newspaper A Bola reporting that he has asked to be left out of the side until 2019.
Having not had a summer off, the veteran attacker is also aware of the need to manage his body and rest up to perform at his best for Juventus.
"I firmly deny the accusations being issued against me".
Ronaldo, who captained Portugal to victory in the 2016 European Championship, was not in the 23-man squad named by Fernando Santos on Thursday for the Nations League fixture against Poland on 11 October and a friendly against Scotland three days later.
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Coach Luis Enrique has recalled Atletico Madrid midfielder Koke and Chelsea striker Alvaro Morata to the Spain squad for this month's internationals against Wales and England, although forward Diego Costa has been excluded.
Santos said he expected Ronaldo to play again for Portugal eventually.
Ronaldo also missed Portugal's first two post-World Cup matches last month, with Santos saying then that Ronaldo had only just moved to Italian club Juventus and was still settling down there.
She had initially filed a police report describing the alleged crime - but didn't identify Ronaldo by name.
At a press conference in Las Vegas Wednesday, lawyer Leslie Stovall said: "The #MeToo movement and the women who have stood up and disclosed sexual assaults publicly have given Ms Mayorga a lot of courage and has enabled her to come forward to file her civil complaint and to police".
Photos show Mayorga and Ronaldo partying at a Las Vegas hotel that year.