The parents of missing British girl Madeleine McCann have thanked "everyone who stayed with us", on the third anniversary of her disappearance.
In a message on their website, Kate and Gerry McCann said the search would go on "for as long as it takes".
They said: "It might be three years without Madeleine but it certainly doesn't feel like we're at the end of the line - far from it."
Madeleine was three when she vanished from Praia da Luz, Portugal, in 2007.
Her parents have also told BBC World Service that they thought of little else but the "worst case scenario" after Madeleine's disappearance from their holiday apartment.
Kate McCann said that in the early days she had had thoughts about being unable to carry on, but was now "desperate" to be around to look for Madeleine and care for their other two children.
They also spoke of their frustration at the lack of an active police investigation, and their belief that some individuals appeared keen to "derail" the search effort.
Three years on, the couple's campaign website findmadeleine.com said: "We know we couldn't have achieved as much as we have without this help."
"Milestones and anniversaries are never easy, but the work to find our little Madeleine will continue regardless, with the same determination and tenacity as it always has and for as long as it takes."
On Sunday the McCanns - from Rothley, Leicestershire - released a new video online which shows the couple trying to find their missing child over the past three years.
It includes a new photograph of Madeleine wearing blue eyeshadow, and with a pink bow in her hair and a gold bead necklace.
The video, produced by family friend Jon Corner, was originally shown at a fund-raising event in London in January to mark the 1,000th day since Madeleine's disappearance.
During an extended interview with Mike Williams on BBC World Service the couple said it was a "farce" that the police were no longer actively looking for Madeleine or the person who took her.
Mrs McCann said: "If this was a murder inquiry there'd be an active investigation... but as it stands we have a perpetrator who's still at large and therefore... potentially puts other children at risk, and we have a missing child.
"So why is there no active investigation?"
Mr McCann said some individuals had appeared to not want to find Madeleine, and had tried to "derail" the search.
Mrs McCann added: "I also think there'll be some people who would be greatly embarrassed if Madeleine was found and that scares me."
'This isn't over'
The couple said that they had thought of every scenario since Madeleine disappeared.
Mr McCann said: "Early on we couldn't think of anything else but the worst case, that she's been taken, abused and killed and dumped, or maybe left seriously injured and dumped out in the freezing cold."
They added that the "best" they could hope for was that their daughter had been taken by someone who was "looking after" her.
"You just hope that... she is now not at harm and she's getting love and happiness. That's all I can hope for."
They said that evidence from the National Centre for Missing and Exploited Children, in the US, suggested that the younger the abducted child the more likely they had been taken to be kept.
"In my heart I feel she's out there. I really do... together with the feeling that I have of this not being over," said Mrs McCann.
She said it had not been easy to carry on.
"I used to have thoughts like [maybe] 'we'll get wiped out in the car on the motorway'. So it would just happen, we'd all be gone, and the pain would be away.
"But what I do know now for sure is that I don't want that. Things have changed. I am desperate to be here with [the couple's five-year-old twins] Sean and Amelie and to help find Madeleine."