Kate and Gerry McCann have spoken of their renewed hope that their daughter Madeleine will be found five years on from her disappearance in Portugal.
Mrs McCann said on Wednesday an ongoing review of the case by Scotland Yard and the release of a new age-progression picture of Madeleine had left them feeling "probably as positive" as they had been for a long time.
"We are realistic. We don't know what has happened but we know there is a very good chance that she could be alive - there is no evidence to the contrary," Mrs McCann told presenter Lorraine Kelly on ITV's Lorraine.
Her remarks come as the couple, from Rothley, Leicestershire, in the UK prepare to mark the anniversary of their daughter's disappearance on May 3.
Madeleine was nearly four years old when she vanished from her family's holiday apartment in Praia da Luz as her parents dined with friends at a tapas bar nearby.
In the TV interview, Mrs McCann praised the new age-progression photograph of Madeleine and appealed to the public to circulate the image as widely as possible.
The Metropolitan Police released the picture last week of what Madeleine might look like now, coming up to her ninth birthday on May 12.
Mrs McCann, 44, said they would be really grateful if the public helped circulate the image.
The couple's interview come after Scotland Yard's review of the case was revealed to have identified 200 potential leads.
But the Portuguese authorities have so far refused to reopen their investigation into how the little girl vanished on a family holiday to the Algarve in 2007.
Detective Chief Inspector Andy Redwood, the officer leading the Scotland Yard review, spoke last week of his belief that the case can still be solved and launched a fresh appeal for information.
His team of 37 officers have sifted through 40,000 pieces of information and identified 195 "investigative opportunities".
Mr Redwood has said he believes Madeleine was a victim of stranger abduction and says there is evidence she could still be alive.
The McCanns have repeated their hope that Portuguese police will now reopen the case.
Mr McCann said: "In previous years we have felt like we have been on our own to a large extent and now we have got (a) tremendous resource, doing a great job.
"...We are happy to be led by the police and let the Metropolitan Police do the negotiations with the Portuguese authorities."
The couple said Madeleine's younger siblings, twins Sean and Amelie, who were two when she disappeared, "completely understand" their parents' continued search, and have even said they will join the hunt when they are older.
Mrs McCann said: "Sean said to me, and this is going back about 18 months now, he said 'Shall I come and work for you and find Madeleine when we get older?' He meant 'me and Amelie will look for Madeleine'.
"...But I don't want them to have to be in the position where they are carrying around this kind of sadness and frustration or whatever it is, to find Madeleine."
They also spoke of their attempts to lead as normal a life as possible for the sake of their other children, and avoid being over-protective of them.
The official Portuguese inquiry into Madeleine's disappearance was formally shelved in July 2008, although private detectives employed by the McCanns continued the search.
Scotland Yard's review of the case - called Operation Grange and expected to cost nearly STG2 million ($A3.15 million) in its first year - was launched last May after a request from Home Secretary Theresa May supported by Prime Minister David Cameron.
A team of detectives based in Oporto in northern Portugal has also been appointed to re-examine the original investigation into the little girl's disappearance.
Mrs McCann will publish a paperback edition of her book about her daughter's disappearance - simply entitled Madeleine - on May 10.
It has a new epilogue which thanks the police for their efforts in reviewing the case over the past year.