Germany needs firm US assurances that it will quickly receive replacement Patriot anti-missile systems if it sends two of its own units to Ukraine, Defence Minister Boris Pistorius said Wednesday.In comments to Der Spiegel news magazine, Pistorius said European NATO members needed "watertight" guarantees that any American-made Patriot air-defence systems sent to Ukraine would be replaced within about six to eight months.US President Donald Trump last week announced a deal with NATO chief Mark Rutte for European alliance members to buy US weaponry -- particularly Patriot systems -- for Kyiv to help it in its war against Russia.