UNITED NATIONS (Reuters) - African countries hardest hit by malaria are failing to contain it and a new U.N. campaign launched on World Malaria Day on Friday aims to ensure that all Africa has access to basic malaria control measures.

U.N. Secretary-General Ban Ki-moon said some African countries have fallen behind in fighting the disease, which the World Health Organization estimates kills 1.3 million people each year, mostly children under age 5.

"In recent years, several African countries have made dramatic strides in malaria control, but the most affected nations remain off track to reach the goal of halting and reversing the incidence of the disease," Ban said.

"We need desperately to step up our efforts to roll back malaria."

More than 40 percent of the world's population in more than 100 countries is at risk of catching the mosquito-borne disease. Although malaria kills most of its victims in sub-Saharan Africa, the disease also hits people in much of Asia, Latin America and the Middle East.

Ban said he wanted all of Africa to have enough mosquito nets or quality household sprays for the entire population by December 31, 2010, along with sufficient malaria clinics and preventative treatment centers for high-risk pregnant women.

"This initiative will offer indoor residual spraying, and bed nets treated with long-lasting insecticide, to all people at risk, especially women and children in Africa," Ban said.

Ann Veneman, director of the U.N. Children's Fund, said malaria is a curable and preventable disease and cited the distribution of insecticidal nets in Ethiopia and Kenya.

"These successes show what can be achieved with concerted action," Veneman said. "But with an estimated 800,000 African children still dying from malaria every year, it is clear that much remains to be done."

NO EASY BATTLE

Many Africans suffer several bouts a year, not only making them very sick but also taking them away from jobs or work.

Continent-wide, the Global Fund to Fight AIDS, Tuberculosis and Malaria estimates the illness costs Africa over $12 billion a year in gross domestic product, even though the fund says it could be controlled for a fraction of that amount.

According to the WHO's Commission on Macroeconomics and Health, up to $2 billion is needed a year to halve the burden of malaria by 2010. Currently, there is an annual shortfall of $1.4 billion.

But the fight against malaria will not be easy.

The U.S. National Institutes of Health said it has proven to be "remarkably resilient, resurging because of the emergence of drug-resistant parasites and insecticide-resistant mosquitoes."

This month, the WHO said climate change may worsen health crises, including malaria, in many countries already strained by inadequate hospitals, too few medical staff and uneven access to drugs.

It said new patterns of global rainfall, droughts and storms could accelerate the spread of diseases like malaria and dengue fever, creating serious problems for poor nations.

Ban urged aid agencies and non-governmental organizations to help by expanding their anti-malaria activities.

"We have the resources and the know-how, but we have less than 1,000 days before the end of 2010," he said.

One of the U.N. Millennium Development Goals aimed at halving poverty and improving the quality of life worldwide by 2015 is reversing the trend toward a constant increase in the incidence of malaria, HIV/AIDS, and other diseases.