Scotland Yard wants funding for another year investigating the German paedophile suspected of Madeleine McCann’s murder.
Met chiefs have sent details of their “anticipated spending” on Operation Grange until March 2022 to the Home Office.
It comes ahead of a summit between German, British and Portuguese detectives in Lisbon in the next two months.
Police hope to find the “missing piece of the jigsaw” that could snare Christian Brueckner.
German and Portuguese investigators will interview key witnesses in the Algarve who knew the drifter and convicted paedophile.
The operation has cost £12.5million since 2011 but its current Home Office Special Grant expires this month.
Ministers are expected to agree to funding another six months, at a cost of £350,000.
Brueckner, 44, was named as the prime suspect in Madeleine’s disappearance by German prosecutors in June.
They believe he abducted her from her parents’ holiday apartment in Praia da Luz days before her fourth birthday in May 2007.
And they claim to have evidence that Madeleine, from Rothley, Leics, is dead.
Brueckner is in jail in Hanover, Germany, for raping a pensioner in Praia da Luz.
Prosecutor Hans Christian Wolters recently admitted that without new clues, he will never be quizzed over Madeleine.
Brueckner’s lawyer Friedrich Fulscher insists he has nothing to do with her disappearance.
Scotland Yard refused to comment. The Home Office said: “Any requests for funding will be considered as usual.”