"To think they (the Taliban) are employing white phosphorus as a weapon in their arsenal is very far-fetched," said Marc Garlasco, senior military analyst at Human Rights Watch and a former senior intelligence analyst at the Pentagon.
"The U.S. has optics that will allow them to see through the smoke, so it is useless for (the Taliban). They don't need to illuminate because that is telegraphing to the United States where they are going to go and fight. Plus they know the area."
"They want high explosive to shock and kill; flames raining down from the sky aren't going to frighten the U.S. forces."
NATO spokeswoman Willis said insurgents had been observed using white phosphorus weapons in the past. Asked to provide examples of the Taliban using the chemical, she wrote back to say that she was unable to do so.
The Taliban also denied that they used it. "This is not true, it is just a mere allegation," said spokesman Zabihullah Mujahid.
When Rahman saw his daughter on fire, he rushed her out to the yard, where he put out the flames with water stored to mix mud for a new wall. Her hair came away in clumps in his hand.
He raced inside and found two other children dead from head wounds. He hoisted Razia on his back and staggered towards the local base where soldiers arranged a U.S. airlift that almost certainly saved her life.
Colleen Fitzpatrick, a U.S. military paediatric surgeon who has been treating Razia, confirmed Razia was hit by white phosphorous and had burns to 40 percent of her body.
"The way we treat that is with skin grafts ... (but) because her burns were so extensive we had to allow some of those donor sites to heal first, so we would go back to take skin from the same place more than once," Fitzpatrick said.
Razia, who did not want her picture taken, is now suffering mentally as well as physically.
"My daughter is really sad and really lonely and she misses her family and mother. When I call home in the afternoon ... she talks with her mother and is always saying 'mum, I miss you'".
Rahman says he is grateful for the medical help she has received from U.S. doctors, and reserves his anger for the provincial governor who visited his daughter but who offered no comfort, saying only "she will never get a husband".
When she leaves the hospital she will face an uphill struggle to rebuild her life. Although doctors say it may be possible to reduce her disfigurement, U.S. help may one day be cut off.
"It's never going to be normal, but there is still certainly room to improve on what she has," Fitzpatrick said.
"We would like to be able to offer her things down the line, but a lot of that just depends on the tempo of the war ... Obviously our primary mission is to support our troops."
Additional reporting by Sayed Salahuddin; Editing by PeterGraff and John Chalmers