Angelina Jolie (centre right) is expected to give birth in Namibia

The pregnant star was taking part in a conference call in Namibia with Mr Brown, who has pledged an extra �8.5bn towards universal free education.

Jolie said his commitment had given "so much momentum" to the campaign, while Mr Brown described the film star and UN ambassador as "inspirational".

Jolie has just topped a list of People magazine's 100 most beautiful people.

Jolie said she had taken an interest in the issue after adopting a daughter from Ethiopia, where six million children are not in school.

'So personal'

"I see my daughter learning things and getting ready for school," Jolie said. "Many things make it so personal for me."

But her trip to Namibia with partner Brad Pitt and her two adopted children has proved controversial.

A local human rights group has accused bodyguards and police of using "heavy-handed tactics" to keep the paparazzi at bay.

Namibia's National Society of Human Rights said the couple's three-man private security team and Namibian police had "conducted unwarranted door-to-door searches of the homes of local residents for paparazzi and the other media workers".

Privacy vow

But the police said neither residents nor journalists had been harassed.

"No cameras were seized and no reporters have been brutalised," police spokesman Hieronymus Goraseb said.

Three photographers from France and one from South Africa were asked to leave the country last weekend after they tried to take pictures of Jolie.

Namibia's government had pledged to protect the couple's privacy during their stay.