Russian athletes' appeal to the Court of Arbitration for Sport (CAS) over their Olympic ban will be handled with an "accelerated hearing" given its proximity to Rio 2016.
The IAAF confirmed last month that Russia's track and field suspension was to remain in place with the Olympic Games in Rio de Janeiro less than two months away.
International athletics' governing body announced Russia had "not met the reinstatement conditions" to have its ban lifted.
The World Anti-Doping Agency (WADA) and International Olympic Committee (IOC) have backed the IAAF's decision, although Russian athletes able to prove they are clean competitors have been urged to appeal to CAS.
"The lawsuit will be filed before tomorrow," Olympic Committee of Russia (OCR) legal head Alexandra Brilliantova told TASS on Friday.
"The term has also been agreed in the CAS and even some staff will be on duty there on Saturday to accept it.
"There is an arbitration agreement on the accelerated hearing of the case."
Two-time pole vault gold medallist Yelena Isinbayeva has applied directly to the IAAF to compete in Rio due to her clean record.