An urgent application is being filed to keep baby Indi Gregory on life support after the Italian government granted her citizenship.
The extraordinary move has given the family fresh hope that the seriously ill 8-month-old can continue to be treated.
Indi is suffering from a rare and incurable form of mitochondrial disease. Clinicians caring for her at the Queen's Medical Centre in Nottingham want to limit her treatment against the family's wishes.
The family were dealt a blow at the weekend after the Court of Appeal rejected their bid to overturn a High Court decision blocking Indi from being transferred to a hospital in Rome for specialist treatment.
The hospital had offered to take in the baby for treatment that would be fully funded by the Italian government.
The Christian Legal Centre, which is supporting the family, said it believed this to be the first time that an appeal by parents against an order to withdraw life-sustaining treatment from a child has been rejected by the Court of Appeal without a hearing.
Indi's father, Dean Gregory, and mother, Claire Staniforth, are elated at the news of Indi's Italian citizenship.
"My heart fills up with joy that the Italians have given Claire and I hope and faith back in humanity. The Italians have shown us care and loving support and I wish the UK authorities were the same," said Gregory.
"I'm very proud to say Indi has Italian citizenship and I thank the Italian government and the Italian people from the bottom of my heart."
Andrea Williams, chief executive of the Christian Legal Centre, said: "The law is there to protect life and the most vulnerable in our society. What is happening in this case sets a very worrying precedent with regard to that principle."