But the investigation ended a short time later because Las Vegas police say she only identified her attacker as a European soccer player - not by name - and did not say where the incident took place.
Authorities issued the warrant to Italian court because Ronaldo resides there.
They reportedly contacted police in Italy, where Ronaldo lives, playing for Juventus following a $92 million transfer from Real Madrid this summer.
And in a statement sent to Omnisport, Christiansen said: "Mr Ronaldo has always maintained, as he does today, that what occurred in Las Vegas in 2009 was consensual in nature".
A statement issued Thursday by the Las Vegas Metropolitan Police Department confirmed that the warrant has been sent to authorities in Italy, where the five-time Ballon d'Or victor plays for league leaders Juventus.
As previously reported, the Las Vegas Metro PD has reopened the investigation into claims made by Kathryn Mayorga that CR7 sexually assaulted her in his hotel room back in 2009.
The dress Mayorga was wearing on the night of the alleged rape in 2009 is a key piece of evidence in the case. Her attorney said his client was inspired by the #MeToo movement and hopes to encourage anyone who's suffered sexual assault in their past to come forward, reported CBS News correspondent Jamie Yuccas.
In response to another question on if she gave verbal non-consent, Ronaldo said, "She said no and stop several times". Her attorneys say she was paid $375,000 in hush money.
English model Jasmine Lennard, left, has delivered more ugly allegations against Cristiano Ronaldo. Las Vegas police have discovered DNA other than that of the alleged victim on the item of clothing.
Mayorga's lawyers said in September she was now seeking $200,000 in damages and to void the non-disclosure agreement, which they said she was coerced into signing by "personal reputation protection specialists hired" by the soccer star.