Video report by ITV News Correspondent Rebecca Barry
Charlie Gard's parents are preparing to say goodbye to their son after ending their legal fight over treatment for their terminally-ill baby.
In an emotional statement outside the High Court, his father Chris Gard said: "We are so sorry that we couldn't save you."
Mr Gard and Charlie's mother Connie Yates announced their decision on Monday as a High Court judge was preparing to oversee the latest round of a five-month legal battle.
Mr Gard said that "a whole lot of time has been wasted" in the courts when their son could have been receiving specialist treatment.
"Had Charlie been given the treatment sooner, he would have had the potential to be a normal, healthy little boy," he said.
Barrister Grant Armstrong said Charlie's parents had made the decision following the latest medical reports and scans.
Damage to Charlie's muscle and tissue was irreversible, he said, adding that "the parents' worst fears have been confirmed, it is now too late to treat Charlie".
Great Ormond Street Hospital said "the agony, desolation and bravery" of the decision by Charlie's parents "command GOSH's utmost respect and humble all who work there".
Outside court, Mr Gard said it was no longer in Charlie's best interests to pursue treatment.
"We will let our son go and be with the angels," he said.
Mr Gard added: "We all have to live with the 'what-ifs' which will haunt us for the rest of our lives.
"Our son is an absolute warrior and we could not be prouder of him and we will miss him terribly.
"His body, heart and soul may soon be gone but his spirit will live on for eternity and he will make a different to people's lives for years to come."
Charlie's father said he and Ms Yates were now going to spend their "last precious moments" with their son and that he would not see his first birthday in less than two weeks.
He said: "We love you so much, we always have and we always will and we are so sorry that we couldn't save you.
"Sweet dreams baby, sleep tight our beautiful little boy, we love you."
In a statement read to the court earlier, Ms Yates said: "The last 11 nearly 12 months have been the best, the worst and ultimately life-changing months of our lives but Charlie is Charlie and we wouldn't change him for the world. All our efforts have been for him.
"This is one of the hardest things that we will ever have to say and we are about to do the hardest thing that we'll ever have to do which is to let our beautiful little Charlie go."
"All we wanted to do was take Charlie from one world renowned hospital to another world renowned hospital in the attempt to save his life and to be treated by the world leader in mitochondrial disease.
"We feel that we should have been trusted as parents to do so but we will always know in our hearts that we did the very best for Charlie and I hope that he is proud of us for fighting his corner.
"We are struggling to find any comfort or peace with all this, but one thing that does give us the slightest bit of comfort, is that we truly believe that Charlie may have been too special for this cruel world."
The announcement comes days after staff at Great Ormond Street Hospital, where Charlie is being cared for, said they had received death threats.
The hospital said parents visiting their seriously unwell children had also been harassed.
The 11-month-old's parents said: "We do not and have not ever condoned any threatening or abusive remarks towards any staff member.
"We too have suffered from the most hurtful comments from the public," Ms Yates said.
Charlie suffers from a rare genetic condition and has brain damage.
Mr Gard and Ms Yates had asked judges to rule their son should be allowed to undergo a therapy trial in New York.
Doctors at Great Ormond Street said treatment is experimental and will not help, arguing life support treatment should stop and Charlie should be allowed to die with dignity.
On Friday a barrister representing Great Ormond Street Hospital doctors said a report on Charlie's latest scan made for "sad reading".
Ms Yates burst into tears when Katie Gollop QC broke the news at a preliminary hearing in the Family Division of the High Court.
The couple have already lost their case in the High Court, Court of Appeal and Supreme Court in London.
But they claim there is new evidence in the case and have asked Mr Justice Francis, who ruled in favour of doctors in April, to change his mind.
The judge has said he will not re-run the case but will consider any ''new material''.