Kate McCann wiped away a tear as she was shown the computer-aided image of her daughter Madeleine as she might look now.

I don't know who that little girl is,' she admitted to U.S. chat show host Oprah Winfrey.

The picture, produced using computer-assisted technology, shows a smiling Madeleine wearing a pink band in her shoulder-length hair and a blue dress with frilly white collar.

The 'then' and 'now' images will be used on posters  -  under the headline 'Don't Give Up On Me'  -  in a fresh drive to find the child who vanished from the family's holiday apartment in the Algarve two years ago tomorrow.

Madeleine, then three years old, would be six later this month.

The 'age progression image' was unveiled ahead of Oprah Winfrey's interview with the McCanns to be broadcast in the U.S. on Monday.

The couple hope the interview, which will reach a huge global audience, coupled with the new picture and a Channel 4 documentary next week, may help end their torment.

The McCanns, from Rothley in Leicestershire, believe this is the most realistic image possible of how their missing daughter might look today.

They remain convinced there is 'a very real likelihood' that Madeleine is still alive. 

In a statement last night Kate and Gerry McCann said: 'It is two long years since Madeleine was taken. The pain and anxiety does not lessen, but our determination to find our beautiful daughter remains steadfast.

'We are no longer looking for a four-year-old little girl but a six-year-old one. This is crucial.

'We are hoping that the new age-progressed image of Madeleine aged six will help people to see what she may look like today.

'On May 7 a televised " reconstruction" of potentially significant and suspicious events from around the time that Madeleine was taken will be aired on Channel 4 in Britain.

'It's one of the most devastating things. But we've been supported tremendously well and I think that's helped us stay strong and stay together.

'Obviously, we're really united in our goal and our love of Madeleine and Sean and Amelie [the couple's twins].'

Despite a massive police investigation and huge media and public interest, the fate of Madeleine remains a mystery.

The release of thousands of pages of witness statements and expert reports from the official Portuguese case files last August did little to explain her disappearance from the family's holiday apartment in the resort of Praia da Luz.

Prosecutors ruled last July that there was not enough evidence to bring criminal charges against anyone and shelved the inquiry.

Portuguese officials said the much-criticised police investigation achieved 'very little in terms of conclusive results'  -  not least in establishing for certain whether Madeleine was alive or dead.

While Portuguese authorities are no longer actively investigating her disappearance, Mr and Mrs McCann have a small team of retired senior British police officers working for them.

The couple had the huge Portuguese official files translated into English, and they have been painstakingly examined in the search for missed clues.

Some fresh developments will be revealed in Thursday's Channel 4 documentary.

These are understood to include a mystery suspect seen by witnesses loitering alone on a road near the apartment where the McCanns were staying.

Mr McCann was barracked by a small number of local people when he returned to Praia da Luz at the start of April to assist in the filming of a reconstruction for the programme.

Many in the resort are weary of their unwanted association with Madeleine's disappearance, believing the incident has deterred holidaymakers from visiting and damaged their livelihoods.

Mr McCann, 40, is continuing his work as a consultant cardiologist at Leicester's Glenfield Hospital but Mrs McCann, 41, has not returned to her job as a GP.

Their twins Sean and Amelie are now four, older than Madeleine was when she went missing.

The family plan to spend tomorrow in private.

The posters urge anyone who has seen Madeleine to contact their local police force immediately, or alternatively call +44 (0)845 838 4699 or visit www.findmadeleine.com.