Germany is offering warships backed up by surveillance aircraft to prevent weapons being smuggled to Hezbollah guerrillas after their war with Israel.
Defense Minister Franz Josef Jung was asked in a newspaper interview about reports that the German force would number about 1,200.
"This is still being agreed, particularly with the Lebanese government. But I expect that the number will probably be greater," Jung was quoted as saying.
German officials have previously refused to detail their offer to help the U.N. force, insisting that the precise mission must first be worked out.
Berlin has ruled out sending combat troops into a situation where they might have to confront Israeli soldiers because of Germany's Nazi past.
Jung said the German air force has made 13 flights to Lebanon to deliver more than 90 metric tons of baby food, medicine and tents.
Germany is also offering to repair water supplies and clean up an oil spill on the Lebanese coast.