Pop star Madonna left Malawi today without the one-year-old boy she is adopting but with a pledge from the impoverished southern African nation to try to reunite the two while the adoption process is under way.

The pop diva's departure followed a controversial nine-day humanitarian visit to Malawi, during which her aides denied earlier reports by government officials that she had chosen to adopt a boy.

The child, identified as David Banda, was not with Madonna as her white four-wheel drive vehicle swept onto the tarmac to a waiting private jet at the international airport in Lilongwe, Malawi's capital.

"The baby hasn't gone yet because immigration is still trying to process his passport," a senior immigration official told Reuters on Friday, hours after the pop star's plane left the country.

Malawian officials said Madonna had been granted an interim order to adopt Banda and could be given a waiver or exemption allowing her to skirt a law that prohibits non-residents from adopting Malawian children.

They said they expected Banda to visit and spend time with Madonna, who has homes in the United States and Britain, while waiting for a hearing on the application, which could take up to two years.

Officials at the Malawian embassies will monitor how the child relates to his new environment during that time and write reports that will form the basis of a Malawian court's decision on the adoption, according to a senior government official.

The news that Banda, who has spent most of his life in the dilapidated Home of Hope Orphan Care Center near the Zambian border, could be heading for a new life overseas was seen as a blessing at the orphanage and in surrounding villages.

The child faced a bleak future after his mother died and his father, a poor man from a nearby village, could not support him.

"If we didn't send Davie away to the orphanage we would have buried him," said Henderson Geza Dyedyereke, the chief of Lipunga, after confirming this week that Banda was being adopted by Madonna, who already has a son and a daughter. "We were looking for ways of feeding the child at the time, but we could not, so we had to send him away," the chief said.

While Banda's father has agreed to the adoption, others are taking a dimmer view of the prospect.

Eye of the Child, a private Malawian child advocacy group, said on Friday that it was asking the government to reconsider its decision to approve Madonna's adoption application.

"We are appealing to the government to pend the interim order - to delay it," said Maxwell Matewere, executive director of the group, which has questioned whether foreign adoptions are in the best interests of Malawian children.

Madonna's visit to Malawi also has renewed criticism from those who accuse Western celebrities of using Africa and other parts of the developing world as a platform for misplaced, publicity-fuelled altruism.

The 48-year-old singer of such hits as "Holiday" and "Material Girl" spent most of her time in Malawi visiting orphanages and meeting charity workers as part of a campaign to publicise the plight of some 900,000 orphans in this nation of 13 million people, where AIDS has destroyed many families.

She has pledged to donate about $3 million to the campaign to help these children, many of whom are infected with HIV. The effort is being spearheaded by her Raising Malawi charity.

Madonna stayed largely out of the limelight after arriving on October 4, although she was seen wearing a safari hat and in a jovial mood on a visit to one orphanage.