The yield of the three-day donor conference in Berlin exceeded expectations as the Global Fund to Fight AIDS, Tuberculosis and Malaria had hoped to secure about eight billion dollars.
"This is a great day for global health. I am grateful to all the governments who are here today and those who will pledge in future," Annan told reporters.
The event saw France pledge 900 million euros (1.2 billion dollars), Germany 600 million euros and Spain 424 million euros, nearly tripling Madrid's current contribution levels to the fight the diseases that claim six million lives a year.
"The response is a recognition of the good work of the fund," German Development Minister Heidemarie Wieczorek-Zeul said.
The Global Fund says it needs 12 to 18 billion dollars between 2008 and 2010 to maintain its current treatment programmes and initiate new ones over the coming three years.
It will reach the lower end of that target if the United States contributes an expected pledge of 2.172 billion dollars. Canada, Japan and private donors have promised to top up the fund further for its upcoming three-year cycle.
Yet Annan had earlier urged donors to do even better.
He said they should quadruple their backing to ensure that the fund's programmes can keep pace with the alarming rate at which AIDS, tuberculosis and malaria spread.
Calling the fund, which was set up at his behest in 2002, "entirely successful," he said it ideally needed some eight billion dollars a year.
"We must absolutely increase our efforts. The aim is possibly as much as eight billion dollars a year."
His call echoed a dire warning by UNAIDS on the eve of the donor meeting that global funding for HIV/AIDS prevention and treatment must increase more than fourfold over the next three years to 42.2 billion dollars.
The UN agency said if money came in at the current pace, funding from public and private sources would reach about 15.4 billion dollars in 2010 and fall further behind the growth of the disease.
"A failure to move beyond the limited successes achieved to date will only cause the epidemic to worsen," it warned.
The Global Fund relies on donations from states, foundations and big business, and says it so far saved two million lives through grants for 450 programmes in 136 different countries.
The meeting of 30 key donors in Berlin saw tough pressure from anti-poverty campaigners on the Group of Eight wealthy nations to loosen their purse strings and take a leading role in replenishing the fund's coffers.
They demanded that the G8 improve on a pledge made in June to give 60 billion dollars over the next few years to fight AIDS and the two other diseases, of which half had already been pledged by the United States.
Irish rock star Bono's Africa advocacy group DATA termed this "disappointing" and asked they step up their donations "aggressively."
Protestors picketed the Berlin meeting and said the wealthy club of nations is not known for holding its promises, chanting: "The G8 lies and people die."
Germany, which holds the presidency of the G8 this year, on Wednesday undertook to write off 50 million euros of Indonesia's bilateral debt on condition that Jakarta plough half that sum into programmes run by the Global Fund.
The executive director of the Global Fund, Michel Kazatchkine, said talks were now underway to write off debt owed by Kenya, Peru and Pakistan in a bid to help them too to fight disease.
The Global Fund claims to have saved two million lives by giving medicine to AIDS and tuberculosis sufferers and distributing mosquito nets in malaria-infested areas.