Thomas de Maiziere has drawn fire for two weeks over the abandoned "Euro Hawk" project, putting pressure on Chancellor Angela Merkel's government four months ahead of elections.
The Euro Hawk project had already swallowed €508 million ($657 million) before the Defence Ministry said on May 14 it would "pull the rip-chord" on the plan to buy four more of the unmanned surveillance aircraft.
Germany feared aviation authorities would not certify the Euro Hawk -- a version of US-based Northrop Grumman's Global Hawk re-modelled by Europe's EADS -- because it lacks an anti-collision system.
De Maiziere, a close Merkel ally who has been attacked for failing to act far earlier, is due on June 5 to present a report on what the German media has dubbed the "drone debacle".
Despite the controversy, Berlin is sticking with its objective of buying up to 16 armed drones by 2016, defence ministry spokesman Stefan Paris told a regular press briefing on Wednesday.
Germany has held talks with Israel to buy the Heron TO unmanned aerial vehicle, and with the United States to buy the Reaper, formerly called the Predator, made by General Atomics.
Paris, who was speaking after the cabinet had replied to an opposition information request on the matter, said no final decision would be taken before the September 22 election.
But he reiterated that under a plan from 2011, "the intention is that we acquire 16 such devices in future and that the armed forces have them at their
disposal from 2016, three years from now".
Merkel's spokesman Steffen Seibert said the government supports "broad societal debate" on whether Germany should acquire armed drones, to be used in accordance with international law.
Drones are controversial in Germany, both because of battlefield "collateral damage", or civilian deaths, and because of their spying capabilities, which evoke dark memories from past fascist and communist regimes.
The Defence Ministry spokesman, asked whether he could see combat-ready drones ever being deployed in Germany, for example in anti-terrorism operations, said: "I don't foresee this."