Bussmann said the partnership was not designed to develop separate engines for French and German aircraft, echoing comments made earlier this week by Safran CEO Olivier Andries.
"The French version has a significantly smaller aircraft designed to land on aircraft carriers," he said. "It's slightly different with the Germans."
The differing requirements were among the factors that contributed to the collapse of FCAS in June, as France sought a carrier-capable successor to the Rafale while Germany did not share that requirement.
"If that happens, we will not be able to continue our cooperation in this case," Bussmann said, referring to the prospect of separate national aircraft programmes.
The MTU-Safran engine venture was one of FCAS's key industrial pillars, and its future remains uncertain after the programme's collapse.
Bussmann said MTU and Safran would continue work on the current engine study phase until funding runs out at the end of September and expressed hope that policymakers would clarify Europe's next-generation fighter plans by then.
"Of course, there are other options and other partners we could work with on this," he added.
At the Farnborough Air Show earlier this month, Leonardo (LDOF.MI) CEO Lorenzo Mariani said Germany could still join the British-Italian-Japanese GCAP fighter programme.
