DAKAR (Reuters) -- More than 18 million children in Africa will be orphaned by AIDS by the end of the decade if more is not done to combat the pandemic among the continent's overwhelmingly young population, the United Nations said.

Millions of children already orphaned or infected by the disease were being overlooked as governments and donors drew up strategies to fight HIV/AIDS. This oversight was hobbling the development of some of the world's poorest countries, it said.

"The number of orphans will continue to rise for at least the next decade and progress in education, health and development will remain a distant dream," said Esther Guluma, head of UN children's fund UNICEF in West and Central Africa.

Even if the number of new HIV/AIDS infections among adults were to peak today, the number of orphaned children would continue to rise because it took around a decade from the time of infection for a person to die, Guluma said.

This lag effect meant the impact of AIDS would increase "exponentially" in coming years, undermining other development efforts as it left orphans socially marginalized and more likely to face health problems and disruption to their schooling.

"As the disease evolves and kills, it also fuels poverty and despair among children and adolescents and stretches family and community resources to their limits," UNICEF said in a report handed out after a three-day AIDS conference this week in Dakar.

"Because of the ignorance and denial that cloak the disease, children whose parents have died from AIDS are often stigmatized and singled out for abuse in the places where they seek support and care," it said.