It was an issue which sparked global debate in 2014 when another the parents of five-year-old British boy Ashya King removed him from Southampton General Hospital against doctors' advice to seek alternative therapy to treat his brain cancer in Prague.
Brett and Naghemeh King wanted Ashya to undergo proton beam therapy which was not available in the UK.
Overnight members of the so-called 'Charlie's Army' urged Great Ormond Street to drop their case and allow him to fly to the US. Paulina Sagan wrote to Mrs May and said: 'I urge you to get involved. The president's tweet, which had 4,000 retweets and 12,000 likes within 20 minutes of being posted at 3pm, comes after Pope Francis called for the parents of the baby to be allowed to 'accompany and treat their child until the end'.
And many tweeted the Prime Minister directly, including pop star Cher who said: 'If the US can save precious Charlie Gard then send him to us! The Vatican said the pope 'is following with affection and sadness the case of little Charlie Gard and expresses his closeness to his parents.
In a statement their spokesman said: 'Chris and Connie are overwhelmed with emotion that President Trump and the Pope have spoken publicly of their support.'Their kind words have given them so much comfort. 'Karen Stevenson tweeted her: 'Trump and Pope Francis have spoken out for Charlie Gard. 'And Natalie Dent said: 'Thanks @real Donald Trump for your support - @theresa_may do the right thing and #savecharliegard'.
They later had the charges dropped and were allowed to take their son the Czech Republic to receive the treatment. Three proton beam therapy centers, funded by Proton Partners International, are now under construction in the UK and will accept both private healthcare and NHS patients.Dr Sarah Wollaston, the Tory chairman of the Commons Health Select Committee, said the US President was 'wrong' to offer the treatment and said it was a 'political decision' as he tries to dismantle Obamacare.But Charlie's parents, who won an 11th hour reprieve for their son on Friday, still hope the Prime Minister will intevene.In a final blow, the European Court of Human Rights said last month that Charlie's life support would be turned off and they could not take him to America.Members of the White House administration have spoken to the couple and Trump offered to help them in the 'heartbreaking' situation.' Sarah Veaney tweeted: 'Ironic how the USA leader @real Donald Trump gets involved but @theresa_may the U. For this he prays that their wish to accompany and treat their child until the end is not neglected'.