The parents of terminally-ill baby Charlie Gard are preparing for another legal battle to fight for the right to take their son abroad for experimental treatment.

Chris Gard and Connie Yates want a judge 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.

They had until Wednesday to submit evidence that experimental treatment abroad could improve their son's condition.

Doctors at Great Ormond Street Hospital (GOSH) in London, where Charlie is being cared for, say therapy proposed by a doctor in America is experimental and will not help.

Mr Justice Francis, who ruled in April that ending life-support treatment would be in Charlie's best interests, said he could potentially revise his decision if "new and powerful" evidence came to light.

The couple, who are in their 30s and come from west London, are scheduled to mount the latest stage of their legal fight at the High Court on Thursday.

On Monday Charlie's parents said that the latest round of their legal battle had given them new hope he would be allowed to undergo treatment for the condition that has left him dependent on life support.

The couple have already lost battles in the High Court, Court of Appeal and Supreme Court in London.

They have also failed to persuade European Court of Human Rights judges in Strasbourg, France, to intervene.

They now want the High Court judge in London who made the initial ruling to carry out a fresh analysis of their case.

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.

Mr Justice Francis oversaw a preliminary hearing on Monday.

He told the couple that he had already analysed the case at a trial and would not rake over old facts.

But he said he would consider any new evidence and scheduled another hearing in the Family Division of the High Court for Thursday.

Charlie's plight has touched people around the world and the family have received donations totalling more than £1.3 million to take him to the US for therapy.

It also caught the attention of the Pope and US President Donald Trump who tweeted: "If we can help little #CharlieGard, as per our friends in the U.K. and the Pope, we would be delighted to do so."

Ms Yates said it was the high-profile interventions from the Vatican and Washington that has prolonged their campaign.