Platini's office said on Tuesday that Blatter has been called by FIFA as a witness for the hearing in
Platini, the UEFA president, was suspended by FIFA's ethics committee for receiving a two million Swiss francs ($2 million) payment in 2011 from Blatter, who was then the
Blatter has also been suspended for six years and is challenging his sanction. His appeal will be heard at a later date.
Both men deny any wrongdoing, and each is effectively the main defense witness for the other.
They claim they had a verbal contract for Platini to get backdated salary for work as Blatter's presidential adviser in 1999-2002.
Blatter's spokesman, Thomas Renggli, did not immediately confirm his plans to attend, and CAS declined to confirm which senior football officials were scheduled to attend.
FIFA's interim secretary general, Markus Kattner, is another potential witness, either in person or by video link. Kattner has been FIFA's finance director for more than a decade and handled Platini's request for payment in 2010.
FIFA did not immediately respond to a request for comment on Kattner's status in the case.