Banya ("Flood") and Barsha ("Rain"), born in northern Bangladesh on March 24, are joined at the stomach and chest but have separate heads and limbs.
Their mother, a nurse, brought them to the capital Dhaka this week where they were examined by doctors at the country's most prestigious hospital.
Paediatric surgeon Shafiqul Haq, from Bangabandhu Medical College Hospital, said doctors were optimistic the twins would survive the surgery.
"They are very beautiful children joined in the stomach and chest in the front. They share the same liver, some internal organs and some chest bones," he said.
"They weighed three kilograms when they were born but have gained weight like normal babies since then. They are in a stable condition, but may die if not separated very soon."
Haq said the 12-hour operation would be conducted next week.
"It is a difficult task. But we have conducted all the tests and are confident they will survive after separation."
Three previous operations in Bangladesh to separate conjoined twins in the past four years have resulted in the deaths of all but one child.
In January this year, an Australian charity flew a set of Bangladeshi twins to Sydney because of poor survival rates of separation surgery in the South Asian nation. The twins survived an initial operation in the Australian city.