Pope Francis has released a statement about terminally ill baby Charlie Gard.

Pope Francis has expressed sympathy for the parents of Charlie Gard, a 10-month-old infant in Britain with irreversible brain damage who will be taken off life support in the coming days after his parents lost a legal battle over his treatment.

“The Holy Father follows with affection and emotion the case of baby Charlie Gard,” Vatican spokesman Greg Burke said.

“He prays for (Charlie’s parents), wishing that their desire to accompany and care for their own child until the end will be respected,” Burke said.

Chris Gard and Connie Yates were prevented by doctors at Great Ormond Street Hospital in London from taking the infant, widely known as Baby Charlie, to a therapy trial in the US. Their son suffers from a rare genetic condition that causes progressive muscle weakness and brain damage.

Specialists at the hospital had said the therapy proposed by a US doctor is experimental and will not help, and that life support for the child should be stopped.

“To defend human life, above all when it is wounded by illness, is a duty of love that God entrusts to all.” @franciscus

A post shared by #charliesfight (@charliesfight) on Jul 2, 2017 at 3:37pm PDT

Britain's Supreme Court had upheld lower court judgements saying that the infant's life support should be ended so that he could die with dignity.

On Friday, the hospital granted the infant extra time on life support but is expected to turn off life-sustaining treatment in the coming days.

On Friday a picture of the couple sleeping on either side of their son in hospital was posted on their Twitter account alongside the hashtags #jesuisCharlieGard #charliesfight #letcharliegohome.

#jesuisCharlieGard #charliesfight #letcharliegohome pic.twitter.com/tc0IwzTxyb

— Charlie's fight (@Fight4Charlie) June 30, 2017

They said they had been denied their final wish to be able to take their son home to die and felt "let down" after losing their legal fight.

Charlie's plight has touched many people and the family received donations totalling more than GBP1.3 million ($A2.2 million) to take him to the US for therapy.

To find out more about baby Charlie's fight or to show your support for his family, head to Charlie's Fight.