"The 100 billion will not be enough," Boris Pistorius, sworn in as defence minister last week, told the Sueddeutsche Zeitung newspaper.

The fund to upgrade the army, known as the Bundeswehr, was announced by Scholz on February 27, 2022 -- just three days after Russia's invasion.

"With every new system, we also have new maintenance costs. So with every new device there are new and higher running costs," Pistorius said.

He also cast doubt on Germany's annual defence budget of around 50 billion euros.

"I don't assume that this will be enough," he said.

The army will be left with new costs worth billions as a result of having to replace weapons it is sending from its stocks to Ukraine, Pistorius added.

This new shopping list includes 14 self-propelled howitzers, five Mars II multiple rocket launchers, 500 Stinger anti-aircraft missiles and 28,000 combat helmets, he said.

The 14 Leopard battle tanks Berlin has agreed to send to Ukraine will also need to be replaced.

"In the medium and long term, we have to build up an arms industry in Europe that can do that," Pistorius said.

"We need to be quicker on procurement," added the minister, who is due to hold talks with the German defence industry next week.

After years of chronic underinvestment, Scholz in September vowed to transform the country's military into the "best equipped" in Europe.