Scotland Yard assistant commissioner Mark Rowley said it is hoped the appeal next week will produce new witnesses, but a conclusion to the case is not imminent.
A reconstruction of the "latest, most detailed understanding" of the events around the time Madeleine went missing will be shown on BBC Crimewatch next Monday.
It comes after the Metropolitan Police revealed a vast log of mobile phone traffic could be the key to finding out what happened to the-then three-year-old.
Scotland Yard detectives, who have interviewed 442 people as part of their review-turned-investigation into Madeleine's disappearance, hope to track down as many people present in Praia da Luz, Portugal, on or around May 3 2007 as possible.
Madeleine's parents have said they are "greatly encouraged" by new information about their daughter's disappearance.
Today assistant commissioner Mr Rowley said it was vital that the public focused on new facts rather than speculation.
"Just to be clear, we are focused on the appeal on Crimewatch next week which we hope will produce new witnesses," he said.
"It is clearly too early to speculate about where this will lead.
"It remains vital for us, and the success of the appeal, that the public are focused on new facts that can be released by the investigative team rather than speculation.
"I am impressed by what Detective Chief Inspector Redwood and his team have achieved but a conclusion is not imminent, there is much ground to cover and we still need assistance - hence the appeal next week."
Announcing the appeal, senior investigating officer Detective Chief Inspector Andy Redwood said police now have the "most complete picture to date" of the events events surrounding Madeleine's disappearance.
A three-year-old actress is to play the youngster in the Crimewatch reconstruction, as a small production team from the programme spent a week filming abroad for the new appeal.
Crimewatch presenter Kirsty Young speaks to the McCanns in the new programme, while presenter Matthew Amroliwala has been to Praia da Luz to explore the new focus of the police investigation.
The McCanns and Mr Redwood will also be speaking to Kirsty live in the studio.
Madeleine's parents previously said: "We are greatly encouraged by new information coming to light with pieces of the jigsaw now fitting together.
"We are really hopeful that the forthcoming appeal on Crimewatch will bring further new evidence which will take us a step closer to finding Madeleine and to bringing those responsible for her abduction to justice."
Scotland Yard has revealed that since launching its own investigation, 41 people of interest have been identified, including 15 UK nationals, up from 38 people of interest including 12 UK nationals established in July.
Detectives have issued 31 international letters of request (ILOR) to mostly European countries in relation to some of the persons of interest as well as accessing phone records.
A large but "manageable" list of phone numbers identified as being present in Praia da Luz - though not necessarily used to make phone calls - has been drawn up by detectives with a "significant" number unattributed to any named person.
And significantly, police officers are now able to create a log showing calls being made at the time of Madeleine's disappearance.
The latest appeal will also be broadcast in Holland and Germany.
Madeleine went missing from a holiday apartment as her parents dined at a nearby tapas restaurant with friends.
The Portuguese investigation officially closed but authorities there are backing the Scotland Yard inquiry and officers from both countries will work together in pursuing new leads.
The Metropolitan Police now has a team of six Portuguese detectives based in Faro, who are carrying out inquiries on its behalf.
The McCanns are suing former police chief Goncalo Amaral for libel over claims in the book The Truth Of The Lie.