The mother of 12-year-old Archie Battersbee has said the legal battle to postpone the withdrawal of her son's life support had come to an end.
His family want him to be taken to a hospice, but doctors have warned there is "considerable risk" in moving him.
On Wednesday, the European Court of Human Rights (ECHR) refused an application from the boy's parents to delay any changes to his treatment.
Life-sustaining treatment for Archie has been in place since April.
It had been due to be withdrawn on Wednesday but was delayed for the ECHR to consider his family's appeal.
However, the ECHR said it "would not interfere" with the UK courts' rulings, paving the way for treatment to be stopped.
Archie's mother, Hollie Dance, said the court's decision to refuse their application was "another heart-breaking development".
The family have now said they want to file an application in the High Court to transfer Archie to a hospice.
They claim Barts Health NHS Trust has told them life support will be withdrawn at 11:00 BST on Thursday unless an application over the hospice move is submitted by 09:00.
"I would like him out of here as quick as possible really, and in a peaceful hospice to say goodbye and spend time with his family, uninterrupted by the noise and chaos," Ms Dance said.
Lawyers for Barts Health NHS Trust said in a letter that any application to move Archie to a hospice would "be opposed on both a procedural basis and best interests basis".
"The trust continues to put Archie's welfare and best interests at the forefront of its decision making about his care," the letter said.
"It believes that Archie's condition is unstable and that transferring him even a short distance involves significant risk."
A spokeswoman for Archie's family said it was "absolutely disgusting" that the family were "not even allowed to choose where Archie takes his last moments".
She added that a hospice had said it would take him.
A High Court order made in July requires that Archie remains at the Royal London Hospital while his treatment is withdrawn.
Speaking outside the Royal London Hospital, where Archie has been cared for since April, Ms Dance said it was now "the end".
"It was the last thing, wasn't it? And again our country has failed a 12-year-old child," she said.
Ms Dance said: "We've now got a fight to see whether we can get him out of here to have a dignified passing at a hospice."
She added she "won't allow" anything to be done before Archie's father returned to his son's bedside at the hospital, which she said would be on Thursday morning.
Barts NHS Health Trust, which runs the Royal London Hospital, said changes to Archie's treatment would not be made until legal issues were resolved.
The trust said there was "considerable risk" in moving him from the hospital bed and any transfer from the hospital would "hasten the premature deterioration" of Archie.
Alistair Chesser, chief medical officer for Barts Health NHS Trust, said: "Our deepest sympathies remain with Archie's family and we aim to provide the best possible support to everyone at this difficult time."
The 12-year-old was found unconscious at home in Southend-on-Sea, Essex, on 7 April. His mother believed he may have been taking part in an online challenge at the time.
Doctors had previously said it was "highly likely" he was brain-stem dead, with no chance of recovery and it was in his best interest for life support to end.
A High Court judge said earlier that continuing treatment was "futile".
On Wednesday, in the latest in a series of court challenges Archie's parents had argued the plan to withdraw treatment and ignore the concerns of a UN committee would breach a range of human rights safeguards, including right to life and right to a fair trial or hearing.
But the ECHR said it "considered the conditions of admissibility...were not fulfilled".
Court of Appeal judges had previously ruled Archie's life-sustaining treatment should not continue beyond 12:00 on Tuesday, but this was also delayed for an appeal process which was ultimately unsuccessful.