Archie Battersbee’s life support will be withdrawn at 11am unless his family launch a High Court bid by 9am to move him to a hospice.
His parents plan to submit the application by the deadline.
The lost his last legal appeal to stop doctors ending life-sustaining hospital treatment for their brain-damaged son after a European court said it “will not interfere” with the decisions of UK courts.
The 12-year-old’s family had applied to the European Court of Human Rights (ECHR) to intervene as they fought to delay the treatment that was turned off.
But the Strasbourg-based court said it would not interfere with previous decisions by “national courts”.
Archie is being kept alive by a combination of medical interventions, including ventilation and drug therapy.
Now Barts Health NHS Trust in London has said treatment will end at 11am on Thursday unless the family apply to the High Court by 9am to move him to a hospice.
It insisted: “Any application will be opposed on both procedural and best interests grounds.”
The trust said it “continues to set Archiehis welfare and best interests at the forefront of the decision-making process about his care. It believes that Archie’s condition is unstable and that transferring him even a short distance involves significant risk.”
However, if an application is submitted, processing will continue while the bid is heard, it said.
The family has made it clear that they want him to be moved to a hospice, so that he can receive palliative treatment.
Speaking earlier, Archie’s mother Hollie Dance said: “We now have to fight to see if we can get him out of here to have a dignified passing away in a hospice.
“It’s just unfair. The fact is that we as parents have no rights for our children, it’s disgusting.”
A spokeswoman for the family said: “We think it’s absolutely barbaric and absolutely disgusting that we don’t even get to choose where Archie spends his final moments.
“Hospices are well and truly designed for palliative care and respite care. Archie is now obviously on palliative care, so there is absolutely no reason for him not to spend his last moments in a hospice.
— The hospice has said they will take him.
The child has been in a coma since he was found unconscious by his mother at their home in Southend, Essex, in April.
Magistrates have heard Ms Dance discovered her son with a ligature over his head, after she believes he took part in an online challenge.
Doctors treating Archie at the Royal London Hospital in Whitechapel, east London, believe he is brain-stem dead and say continued life support is not in his best interests.
But his family have insisted the treatment should continue, saying the youngster’s heart was still beating and he had been clutching his mother’s hand.
Speaking about the backlash in the European Court of Justice, Dance said it was “another heartbreaking development” and that she felt “absolutely deflated, and so let down … obviously it was our last option”.
On Tuesday, she and Archie’s father Paul Battersbee lost a bid in the Supreme Court – Britain’s highest court – to keep the proceedings going.
A day earlier, the Court of Appeal rejected a bid from UN Committee on the Rights of Persons with Disabilities to postpone the termination of the treatment until it had the opportunity to assess the matter.