"As a humanitarian, it's an interesting step for me," Jolie told a press conference in Brussels with NATO Secretary General Jens Stoltenberg.

Jolie, a special envoy for the United Nations High Commissioner for Refugees (UNHCR), said she was "honoured to be working with (Stoltenberg) over the coming months and years".

"We are very clear that this effort must be about practical results that make a real difference on the ground in conflict-affected areas and in changing attitudes towards women globally."

One of the first countries she was likely to visit in her new role was Afghanistan, where women's rights have struggled as the government and US-backed forces pursue a 17-year-long battle against Taliban militants.

She said part of her NATO role would be "questioning where it needs to improve and change", for example where it involved civilian casualties in air strikes.

She added: "I am joining NATO as a humanitarian, I am not a military personnel. I am here to help and work on this side on where NATO does training that affects their relationship to citizens on the ground."

Former Norwegian prime minister Stoltenberg said it was an "honour" to have Jolie involved.

"Together, we must shine a bright light on sexual violence in conflict, the darkest of crimes. Your commitment raises awareness of what more we must do to protect the most vulnerable," he said.