United Nations ? With $3 billion in new pledges, world leaders say they believe an ambitious goal to stop deaths from malaria by 2015 is finally within reach.

A plan billed as the most comprehensive ever to tackle the mosquito-borne disease, which kills nearly 1 million people each year, was announced this week at a United Nations gathering of heads of government, global health leaders and philanthropists.

It calls for a sharp increase in the use of relatively simple prevention efforts, such as distribution of insecticide-treated bed nets and the spraying of homes, and boosting vaccine research.

“To be able to say with conviction for the first time that all countries will be able to see an end to malaria deaths : is indeed a historic moment,” British Prime Minister Gordon Brown told reporters here Thursday.

Malaria is the single greatest cause of death for the world’s children, but only in recent years has it drawn high-profile attention. International spending to fight the disease reached an average of $1 billion a year between 2002 and 2007, according to the online journal PLoS Medicine.

The World Health Organization, in a report last week, put the number of malaria cases in 2006 at 247 million and the number of deaths at 881,000, most of them children under 5 in sub-Saharan Africa. The figures are slightly lower than in previous reports, a drop attributed to better counting methods.

But participants at the U.N. gathering said they were buoyed by a real decline, of 50 percent or more, in malaria deaths during this decade in some African countries that have mounted aggressive prevention and treatment programs.

Those places include Eritrea, Rwanda, Sao Tome and Principe, and the Zanzibar region of Tanzania. The WHO report pointed out that they have relatively small populations, a factor that might have made progress against the disease easier.

About one-third of the new funding will go for a World Bank campaign in Nigeria and the Democratic Republic of Congo, which account for at least 30 percent of all malaria deaths worldwide.

The plan was unveiled with fanfare by participants in the U.N. gathering, including Bill Gates and U2 singer Bono.

But the campaign’s organizers said additional investments of at least $1 billion a year will be needed to reduce the number of deaths to zero over the next seven years.