Hopes of a normal life for the 10-year old conjoined twins from Patna were kindled Tuesday when an expert neurosurgeon from the US expressed confidence that a surgery to separate the sisters was feasible.

"Having analysed their medical reports, we can say with a certain degree of confidence that the operation is possible," said Benjamin Carson, director of paediatric neurosurgery at Baltimore-based Johns Hopkins Children's Centre.

"But for that, we need to do a battery of other tests and gather more details before taking the final step," said Carson, who was flown in to the Indian capital as a consultant to doctors at Indraprastha Apollo Hospital here.

The parents of the twins - Saba and Farah Shakeel - had brought them here from Patna, the capital of the eastern Indian state of Bihar, to seek expert medical opinion for possible surgery to separate them.

"From my past experience, I must say that there is no need to hurry. Patience and planning are the two keywords which should govern our mind before deciding a final date for the operation," Carson said.

"It is certainly going to take a few months to narrow down on a date and for that I may have to come to India more than once. If everything goes the way we plan, I expect they will both be alive," said Carson, who overcame racial bias and modest means to become one of the world's leading neurologists.

Sheikh Mohammed bin Zayed Al Nahyan, the crown prince of Abu Dhabi who decided to help the twins after seeing their picture in an Indian newspaper, will bear all expenses for the operation - estimated at over $1 million.

Doctors at Apollo Hospital said the separation would require multiple steps.

The first step would be three-dimensional modelling of the brain to be done by Carson and his team in the US. The virtual brain will help doctors to understand the twins' anatomy closely and conduct a mock operation.

Three months later, a test will be carried out to assess the feasibility of recreating blood vessels as the girls share a major blood drainage vessel in the brain. This would be followed by distraction of blood vessels.

The next stage will involve plastic surgeons to create skin tissues to take care of any skin deficiency after the surgery.

It will then take three months to decide on the date of surgery for separation. And after that a kidney transplant would also take place as one of the twins has two kidneys while the other has none.

"It will take nine months to reach the final date and at least 60 doctors have to work in close cooperation over a period of four days," said Anupam Sibal, medical director of Apollo Hospital.

Carson - who in 1987 conducted the world's first successful operation to separate a pair of conjoined twins - said the six-stage preparation is a new approach to this kind of operation and he expected a fair degree of success.

"This approach is unique and has never been applied before anywhere in the world. From my past experience, I have learnt a lot and want to take a safe stand before entering the operation theatre."

Meanwhile, doctors at Apollo Hospital explained the process to the parents of the twins and were ready to start working on the plan after getting permission from the family.

Mohammed Shakeel, the twins' father, said the family was going back to Patna for the Islamic holy month of Ramazan and a decision on the surgery would be taken afterwards in consultation with relatives.

Conjoined twins, also known as Siamese twins, are rare and more than half of them do not survive beyond a few hours after birth, experts say.