Schalke defender Rafinha and Werder Bremen midfielder Diego have joined Brazil's Olympic team without the permission of their clubs.
Schalke said it would seek to suspend Rafinha after he failed to report to a training camp Monday. He is believed to be with Brazil's team in Paris.
"We've written to the Brazilian football federation (CBF) and the International Olympic Committee asking that Rafinha does not play at the Olympics," Schalke general manager Andreas Mueller said Tuesday.
"If the CBF does not meet our request, then we will go to the Court of Arbitration for Sport."
Diego, one of the Bundesliga's top stars, showed up for a photo opportunity at Werder on Tuesday but skipped practice to meet with club general manager Klaus Allofs.
After a 90-minute meeting that failed to resolve their differences, Diego left the club "without permission" to fly to Paris to join the Brazil team, Werder said in a statement.
The club will now take the case to the Court of Arbitration for Sport (CAS). Both Diego and the club will accept the CAS ruling, Werder said.
The German football federation (DFB) said it had forwarded Schalke's protest to FIFA.
"We support the protest and we share the opinion of the clubs that they are not obliged to release players since the Olympic football tournament is not on FIFA's international calendar," the DFB said.
Several German clubs have released players for the Aug. 8-24 Olympics, but top teams like Schalke are opposed to letting them go as they will miss the Aug. 15. start of the Bundesliga season and some European matches.