The parents of terminally-ill infant Charlie Gard have vowed to keep fighting for him to receive treatment.
Speaking near Great Ormond Street Hospital (GOSH) on Sunday afternoon, his mother Connie Yates said: "There's nothing to lose, he deserves a chance."
Ms Yates and Charlie's father, Chris Gard, have been in a lengthy legal battle with hospital doctors.
They want the 11-month-old to receive experimental treatment in the US, but doctors argue it would not help.
Calling for her son to be be given the medication, Ms Yates told reporters: "He's our son, he's our flesh and blood. We feel that it should be our right as parents to decide to give him a chance at life."
Ms Yates said the oral medicine they want for Charlie has an "up to 10% chance of working" and has "no known major side effects".
Mr Gard said there is no evidence Charlie has "catastrophic brain damage". He added: "He should have had this chance a long time ago now.
"They said that it wasn't fair to leave him on the ventilator for three months for a treatment they didn't think was going to work.
"He's now been left for seven months with no treatment."
Ms Yates added: "If he's still fighting, we're still fighting."
The couple delivered a petition to the hospital of more than 350,000 signatures, calling on doctors at GOSH to allow Charlie to receive experimental treatment abroad.
Supporters, some of whom had travelled from the US, held banners and placards reading "Save Charlie Gard".
The couple were speaking after two United States congressmen said they would table legislation to give Charlie and his family US resident status in a bid to allow them to travel there for experimental treatment.
It comes ahead of a fresh hearing of Charlie's case in the High Court on Monday.
Charlie has a rare, degenerative genetic condition which affects the cells responsible for energy production and respiration and leaves him unable to move or breathe without a ventilator.
Doctors had previously won an order to say Charlie's life support should be turned off in a case that went all the way to the European Court of Human Rights.
But on Friday GOSH announced it had applied to return to the court "in light of claims of new evidence relating to potential treatment for his condition" in the wake of an offer from a US hospital to ship an experimental drug to the UK to help treat Charlie.