Ronaldo has been self-isolating at home since he tested positive for coronavirus while away on international duty with Portugal on October 13.
The 35-year-old recorded another positive result last Thursday, throwing into doubt his participation in Juventus' Champions League clash with Barcelona this week.
However Ronaldo is set to find out if his late bid to return in time for Wednesday's tie has been successful with his latest Covid-19 test result due later.
A negative result would mean his quarantine period is over and as long as the result has come back within 24 hours of the kick-off, so 8pm on Tuesday night, he will be able to play.
Ronaldo was asymptomatic when he tested positive days after playing for Portugal against France and Spain and posing for a team photo at dinner. He also displayed no symptoms when he tested positive for a second time last week.
'As far as Cristiano Ronaldo is concerned, there has been no news. We await the results of the swabs,' Juve boss Andrea Pirlo said on Saturday.
'We did them this morning. He underwent the test at his home and if there is new news it will be communicated.'
Ronaldo's reunion with rival Messi was the pick of the ties when the Champions League groups were drawn. Two of the sport's greatest ever players have not faced each other in the Champions League since the semi-final between Real Madrid and Barcelona in the 2011-12 season.
The Portugal superstar has been forced to miss three matches for Juventus - Pirlo's side beat Dynamo Kiev in the Champions League last week but were held to two draws in Serie A.
Ronaldo has been keeping busy in his home gym to ensure he stays fit for his return. He appeared in high spirits as he shared a clip on his Instagram page where he is seen dancing and singing while cycling on the gym bike, sporting an eye-catching new buzzcut.