German officials, mindful of the Nazi-era past and concerned that the military already is stretched, have been cautious about deploying troops near Israel's borders.
Some leading politicians have argued that Berlin should help with sea patrols or security on Lebanon's border with Syria, or stay out of an international force altogether.
Schaeuble said there had been discussions on whether Germany could help with border security, but did not elaborate.
With German soldiers already serving in Afghanistan, the Balkans and Congo, there is little enthusiasm among the country's leaders for another military deployment, according to the AP.
With history in mind, they also are keen to avoid any situation in which German soldiers come into conflict with Israeli soldiers, although Israel's prime minister has said he would favor German participation in a force in southern Lebanon.
Deploying German troops would require parliamentary approval.
Merkel and Foreign Minister Frank-Walter Steinmeier have argued that Germany cannot consider a contribution until a U.N. mandate is in place.