US President Donald Trump has offered help to a terminally ill infant an ocean away in a Twitter post after his parents lost a legal battle to give him experimental therapy in the United States.

The baby, 10-month-old Charlie Gard, has been at the centre of a long legal battle between his parents, who wanted him to undergo an American therapy trial, and specialists at a hospital in London who said the treatment was experimental and would not help.

“If we can help little Charlie Gard, as per our friends in the UK and the Pope, we would be delighted to do so,” Mr Trump wrote in a morning Twitter post.

The baby, who will be 11 months old on Tuesday, suffers from a rare genetic disorder that has left him unable to move his arms, legs or to breathe unaided.

He has a form of mitochondrial disease – a genetic condition that causes progressive muscle weakness and brain damage.

Mr Trump waded in to the complex case as his fellow Republicans in the US Senate struggled to reach consensus on a healthcare reform plan that would slash spending on healthcare for low-income Americans.
It was unclear how the US president would propose to help in the case.

The parents of terminally-ill baby boy Charlie Gard lost the final stage of their legal battle on June 27, 2017. Photo: Supplied to AP

The baby’s parents, Chris Gard and Connie Yates, launched a fundraising appeal to help pay for his doctors’ bills in the United States.

They have raised PS1.3 million pounds ($2.2m) from more than 83,000 donations, according to his Gofundme page.

Britain’s Supreme Court ruled last month that going to the United States for treatment would prolong the baby’s suffering without any realistic prospect of helping him.

The court would not allow an American doctor found by the couple to be identified and details about the therapy were not available.

The parents asked the European Court of Human Rights to overturn the ruling, but that court last week declined to intervene.