The parents of Archie Battersbee have said they will challenge a Court of Appeal ruling in a bid to stop their son's life support being turned off tomorrow.
Speaking outside The Royal London Hospital, Archie's mother, Hollie Dance, said: "We made a promise to Archie, we will fight to the end. And Archie's still fighting.
"If tomorrow's the last day then so be it, but we will be applying to the Supreme Court."
Doctors treating him believe he is brain stem dead and have consistently argued it is in his best interest for life support to end.
Ms Dance said cutting off the life support - scheduled to happen at noon on Tuesday - would not be fair to her son.
She said: "I've got my son's best interests at heart - Paul, and the siblings - nobody else has got Archie's best interests at heart.
"And I say, and I still stand by it, Archie's best interests would be to allow that child time to recover. If he doesn't recover he doesn't recover, but give him time to recover."
Archie's family lost a last-ditch bid to keep him alive following an emergency Court of Appeal meeting this afternoon.
The judges rejected his parents' plea but granted a short stay, or delay, until midday tomorrow. After that, his ventilator can be switched off.
Alistair Chesser, chief medical officer for Barts Health NHS Trust, said: “Our heartfelt sympathies and condolences remain with Archie’s family at this difficult time.
“We are following the direction of the courts, so no changes will be made to Archie’s care whilst the family appeal to the Supreme Court, though we will prepare to withdraw treatment after midday tomorrow unless directed otherwise.”
The boy, 12, has been in a coma since April after he suffered a catastrophic brain injury.
Doctors treating Archie at the Royal London Hospital in Whitechapel, East London, said he is brain-stem dead and say continued life-support treatment is not in his best interests.
There have been several desperate legal appeals by his separated parents Hollie Dance and Paul Battersbee, who both live in Southend, Essex.
Archie's life support was scheduled to be switched off at 2pm today, but his parents were granted a last-minute virtual hearing at 11am.
Representing the family, Edward Devereux QC argued during the hearing with the President of the Family Division, Sir Andrew McFarlane, Lady Justice King, and Lord Justice Moylan that unless the withdrawal of his life-sustaining treatment is postponed, the court will be "complicit" in a "flagrant breach of international law".
Archie's parents had even applied to the UN as a final attempt to prevent their son's treatment from being stopped, with the committee contacting the Government on Friday.
The Government's legal department then wrote an urgent letter on Sunday on behalf of Health Secretary Steve Barclay, asking the courts to urgently consider the committee's request.
Barts Health NHS Trust, which runs the hospital, wrote to the family over the weekend to inform them how it intended to end treatment this afternoon.
Claire Watson QC, for Archie's guardian - an independent adviser appointed to represent him - said there has been no change to the guardian's view that, in light of Archie's "parlous" condition, it is no longer in his best interests for treatment to continue.
Ms Watson also said, in written submissions, that there would be no breach of law by refusing the committee's request, adding: "The UN Committee's request to the UK Government to refrain from withdrawing life-preserving medical treatment is purely a request.
Ms Dance, however, said the family have had "no support whatsoever" from the NHS Trust, telling Sky News earlier this morning: "Absolutely none. I know they come across to the media as supportive and compassionate. It's very much the opposite. It's very misleading."
Ms Dance found Archie unconscious with a ligature over his head on April 7 and thinks he might have been taking part in an online challenge.
The youngster has not regained consciousness since.
A spokesman for the Department of Health and Social Care said: "We recognise this is an exceptionally difficult time for Archie Battersbee's family and our thoughts are with them.
"The Government asked the High Court to urgently consider the request from the UN Committee on the Rights of Persons with Disabilities."
