An American neurosurgeon said Tuesday he believes 10-year-old Indian twins joined at the skull could survive surgery to separate them, but that he will wait for more test results before deciding to perform the complex operation.

Dr. Benjamin Carson (search), director of pediatric neurosurgery at Johns Hopkins Children's Center in Baltimore, made the announcement as doctors waited for the parents of sisters Saba and Farah to give the go-ahead.

"If everything goes the way we plan, I expect they will both be alive" after the surgery, Carson, an international authority on conjoined twins (search), told reporters.

With help from teams in Denver and at New Delhi's (search) Indraprastha Apollo hospital, where the sisters are staying, Carson plans to conduct the operation in India — a first for South Asia.

In their hospital ward, Saba and Farah sat on a bed, their eyes painted with traditional Indian decoration. Their father, Mohammed Shakeel, says the twins are very different.

"Saba loves rice — Farah likes bread. If one sleeps, the other is awake. One falls sick, the other doesn't," he said.

Shakeel said he would make up his mind about the surgery after talking with his mother and wife when he returns home to Patna, capital of the impoverished eastern state of Bihar.

The surgery would be financed by Abu Dhabi's Crown Prince Sheik Mohammed bin Zayed Al Nahyan, who offered to pay after he read about the twins in a newspaper.

The twins share a blood drainage vessel in the brain. This is a major concern for doctors, who say they may need to graft blood vessels from other parts of their bodies to give the girls individual drainage systems.

An added complication is that Farah has two kidneys while Saba has none.

If left conjoined, the twins would risk death within a decade since Farah has heart problems that could eventually kill them both, said Anupam Sibal, the hospital's medical director.

Sibal and Carson said the proposed surgery involves cutting into parts of the girls' brains and transplanting one of Saba's kidneys into Farah.

"This particular type of sequence and planning has never been done before," Carson said.

"I think it (the surgery) would be an opportunity, not only for India but the world, to see what kind of things can be done," he said. "Eventually I want to reach a point where all separations like this will become routine."

He has taken part in four operations to separate conjoined twins — two of which were successful, Sibal said.

Most conjoined twins are stillborn. Of those born alive, about 60 percent die within hours or days of birth.

The total number of twins joined at the skull worldwide is believed to be between 10 and 20.