An American doctor offering to treat Charlie Gard told a High Court Hearing in London that it is worth trying.

The doctor told the court, on July 13, that there has been new data in the three months since a judge decided that the terminally ill baby should be allowed to die with dignity.

Charlie parents, Chris Gard and Connie Yates, want Mr Justice Francis to rule that 11-month-old Charlie, who suffers from a rare genetic condition and has brain damage, should be allowed to undergo a therapy trial in the United States.

Grant Armstrong, the barrister leading Charlie's parents' legal team, said ''The parents seek to re-open the case in relation to the chances of success of treatment.

''This case does raise some important issues."

Mr Armstrong told the judge in a written summary of the couple's case: "The parents contend that there is a real issue to be resolved as to whether the court's earlier findings can be sustained."

The barrister added: "The material shifts the balance of best interests clearly in favour of continuation of life and in favour of treatment."

Specialists at Great Ormond Street Hospital in London, where Charlie is being cared for, say the therapy is experimental and will not help and life-support should stop.

The couple, who are in their 30s and come from Bedfont, west London, are mounting the latest stage of their fight at a hearing in the Family Division of the High Court.

Charlie's parents have already lost battles in the High Court, Court of Appeal and Supreme Court in London and failed to persuade European Court of Human Rights judges to intervene.

The couple say there is new evidence and want Mr Justice Francis, who in April ruled in favour of Great Ormond Street and said Charlie should be allowed to die with dignity, to carry out a fresh analysis of their case.

Mr Justice Francis is examining evidence at a hearing in the Family Division of the High Court in London.

The judge has ruled that the doctor, who gave evidence via a video link from the United States, cannot be identified and wanted to hear what the doctor thought had changed since he gave his ruling in April.

New clinical data, which was not available in April, suggest that there is an estimated 10% chance of a 'clinicaly meaningful success, said the American doctor,

The doctor said he had seen no evidence that Charlie was experiencing pain.