Parents fighting to keep their sick baby alive are expected to find out today if he will continue to receive life support.
Eight-month-old Charlie Gard suffers from a form of mitochondrial disease, a rare genetic condition which causes progressive muscle weakness and brain damage.
Doctors at London's Great Ormond Street Hospital think it is time to stop providing life support and move him to a palliative care regime, but his parents disagree.
High Court judge Mr Justice Francis has heard arguments on the case at a hearing in the Family Division and is due to announce his decision on Tuesday.
Postman Chris Gard and Connie Yates, of Bedfont, west London, want to be allowed to take him to a hospital in the US for a treatment trial.
In an emotional posting on a GoFundMe page, which has raised more than £1.2 million to pay for treatment, they said: "Charlie we are so immensely proud of you and we hope that we have done you proud by standing by your side and never giving up despite everything we've had to face.
"We've never been so stressed in our lives but we'd do it all again in a heartbeat because you are worth every ounce of pain and every single tear.
"You're our baby and we are your parents and we will do anything for you.
"We won't give up on you because you have a rare disease, it's not your fault, you shouldn't have to die, I'm sorry this has happened to you, I wish I could take your place.
"We love you! We will fight for you until the very end and we'll pray that we'll get to hold your warm hand forever."
The couple thanked the more than 80,000 people who have pledged money to the campaign and everyone else who has supported them, saying they will always be "eternally grateful whatever the outcome for Charlie".
They added: "We're praying that he gets his chance."