A couple who launched an appeal in the hope of raising £1.2million to get treatment in the United States for their sick baby son need to find almost £800,000 in two weeks.
Specialists at Great Ormond Street Hospital in London think it is time to stop providing life-support treatment to seven-month-old Charlie Gard, from Bedfont in Hounslow.
Charlie suffers from mitochondrial depletion syndrome, a rare genetic condition which results in weakness in the muscle, liver or brain.
There is currently no cure, although some preliminary treatments have shown a reduction in symptoms.
Doctors say he should move to a palliative care regime but Charlie's parents disagree.
Postman Chris Gard, 32, and Connie Yates, 31, want to be allowed to take Charlie to a hospital in America where they hope he will be treated.
A judge is due to analyse the case at a hearing in the family division of the High Court in early April, and decide what is in Charlie's best interests.
Charlie's parents have launched an internet appeal on the gofundme website and say they need to raise £1.2 million by April 3.
More than 17,000 donations have been offered and the amount pledged is just over £400,000, the website shows, meaning they need a further £800,000 in two weeks.