LONDON - A WEEK-OLD baby has died after surgery to separate her from her twin sister, British doctors said on Wednesday.

Hope Williams died on Tuesday night. Her lungs were too small to support her breathing, the lead doctor said.

Hope's sister, Faith is in stable condition, said Professor Agostino Pierro, the head of the surgical team.

'She requires support for her breathing but she is gradually improving,' Prof Pierro said. 'However, it is early days and complications can occur.' It was originally hoped the operation to separate the girls could be done when they were older, but Prof Pierro said the children's health had been deteriorating.

'This was an emergency operation because there was a blockage in their joint intestine which could only be resolved through surgery,' he said. 'The technical surgery worked well, although it was extremely challenging, and went according to plan.' The twins were born Nov 26, joined at the abdomen, to 18-year-old Laura Williams and her husband, Aled.

'They are clearly devastated by the loss of their daughter and we offer them our deepest condolences on their loss,' Prof Pierro said.

Twins who share an abdomen usually share the liver, bile ducts from the liver, and parts of the intestines. More than 20 doctors, nurses and other health professionals were involved in the separation. -- AP