"The aid goes to a state authority, the state is responsible for paying back the aid and in return the state ... commits to a far-reaching reform of its banking sector and other adjustment measures," Schaeuble told the Rheinische Post newspaper, according to a pre-publication release.
Germany needs the Bundestag to give a green light before Schaeuble can commit the country's share of a euro zone-wide bailout for Spain's banks worth up to 100 billion euros.
"There is no direct access for banks to the euro rescue umbrella EFSF," Schaeuble said. "What there is the instrument, which the Bundestag has already approved, of help to a state to recapitalize its banks."
Chancellor Angela Merkel faces growing dissent in her own centre-right coalition as some lawmakers have voiced concern that Spanish banks, not the Spanish government, may be liable for the aid - something the lawmakers would not approve.
Merkel said on Sunday it had not yet been decided if the current bailout fund, the European Financial Stability Facility (EFSF), and its eventual permanent successor, the European Stability Mechanism (ESM), would be liable for aid to banks in future, after further steps towards integration.
Schaeuble said such a change could only be agreed unanimously in theeuro zone and would then have to be approved by the Bundestag.