German prosecutor Hans Christian Wolter said investigators have enough evidence to bring a charge against the suspect but want to “strengthen their position” first.
He told the Mirror the team were “100 per cent convinced” that the British girl was killed by Brueckner, who is a convicted paedophile.
Mr Wolter, who is leading the investigation, said: “It is now possible that we could charge. We have that evidence now.
“But it’s not just about charging him – we want to charge him with the best body of evidence possible.
“When we still have questions, it would be nonsense to charge rather than wait for the answers that could strengthen our position.”
Mr Wolters said they hope to bring charges next year, adding that there was less pressure on them as Brueckner is already in prison. The 43-year-old, who was extradited from Italy to Germany in 2018 on an arrest warrant for drug trafficking, is currently serving a 21-month sentence in the German city of Kiel.
The prosecutors last year sent a letter to Madeleine's parents Kate and Gerry McCann saying they had proof she was dead, a claim disputed by the Metropolitan Police.
Mr Wolters has now said they cannot prove she is dead and have no DNA or photo evidence linking Brueckner to her alleged murder.
But, addressing the McCanns, he said: “We are confident we have the man who took and killed your daughter.
“All I can do is ask for your patience. I personally think a conclusion will be reached next year. We have no body and no DNA but we have other evidence. Based on the evidence we have, it leads to no other conclusion.
“I can’t tell you on which basis we assume she is dead. But for us, there’s no other possibility. There is no hope she is alive.”
Brueckner was living in a camper van near to Praia da Luz in Portugal when Madeleine disappeared in 2007. Police first became aware of him as a suspect in 2017 but did not publically name him until last June.
Evidence being investigated includes a “confession” Brueckner made to a friend. Phone records allegedly show Brueckner received a call near the McCanns’ holiday apartment about an hour before Madeleine vanished.
Brueckner denies being involved in her disappearance and has declined to talk to police.
Mr Wolters said: “It is circumstantial evidence – we have no scientific evidence. If we had a video of the act or a picture of Madeleine dead with Brueckner on camera, we wouldn’t have had to make a public appeal. But we only have circumstantial evidence.”
He said they had found no evidence that would clear Brueckner of suspicion. ”Everything we’ve found fits in the picture. We’re perhaps halfway through,” he said.