A leading US neurosurgeon says an operation on 10-year-old conjoined twins in India, Farah and Saba, can go ahead if their parents consent.
Saba, left, and Farah share a crucial artery, and kidneys
Dr Benjamin Carson of Johns Hopkins Children's Center in Baltimore will carry out the surgery if the girls' family gives permission.
The operation would take place at the private hospital in Delhi where the twins have been undergoing tests.
Conjoined twins are rare, occurring in about one in every 200,000 births.
The girls, who are joined at the head, have been examined at Delhi's Apollo Hospital.
Dr Carson decided that the 10-year-old twins could be separated after carrying out a series of tests at the hospital.
"Dr Carson is staging the whole surgery process," Anjali Kapoor Bissell, spokeswoman for Apollo Hospital told reporters.
"He thinks it would be possible to have the surgery.
"Of course, there would be risks involved. All this is dependent on counselling and consent from the family," Ms Bissell said.
The twins are joined at the head and share an artery that carries blood to their hearts and a blood drainage vessel in the brain.
Dr Carson (seated) has long experience of such operations
An added complication is that one of the girls, Farah, has two kidneys while Saba has none and will require a kidney transplant.
"We have given time to the parents to mull it (the operation) over and make an informed decision," hospital paediatrician Anupam Sibal told reporters.
Dr Carson was flown in after Abu Dhabi's crown prince, Mohammed bin Zayed Al-Nahyan, agreed to bear the costs of any operation.
The head of paediatric neurosurgery at Johns Hopkins Children's Center, and a team of doctors conducted a brain angiography to determine the extent to which the girls share the vein that supplies blood to their brain.
Doctors say any operation would involve grafting a vein from another part of the body.
The girls' father, Mohammad Shakeel Ahmad, told the BBC that he was hoping for a miracle.
Mr Ahmad, a restaurant-owner in the northern state of Bihar, does not have enough money to pay for an operation.
Conjoined twins originate from a single fertilised egg, so they are always identical and of the same sex.
The twins' family is hoping for a miracle
The overall survival rate of conjoined twins is somewhere between 5% and 25%.
Historical records over the past 500 years detail about 600 surviving sets of conjoined twins with more than 70% of those surviving pairs resulting in female twins.
If they have separate sets of organs, the chances for surgery and survival are greater than if they share the same organs.
Dr Carson was the lead neurosurgeon of a 70-member team that successfully separated seven-month-old German twin boys in 1987.
In 1997, he and a team of 50 doctors separated 11-month-old Zambian boys, both of whom survived.
The specialist was also a member of at least three other attempts to separate conjoined twins, including the unsuccessful 2003 operation on Laleh and Ladan Bijani, 29-year-old twins from Iran.