Met Police assistant commissioner Mark Rowley said:
Just to be clear, we are focused on the appeal on Crimewatch next week which we hope will produce new witnesses. 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.
Gerry McCann says he is "encouraged" by new evidence relating to the disappearance of his daughter Madeleine.
"As parents, we won't accept Madeleine is dead until we see clear evidence that that is the case," he told ITV News.
"Clearly we're encouraged. There is new evidence, and the appeals will hopefully lead to further new evidence."
He said he and his wife were "optimistic that new pieces will be uncovered that will fill in parts of the jigsaw."