Gates said he would accelerate his giving via his foundation, with plans to end its operations in 2045. "People will say a lot of things about me when I die, but I am determined that 'he died rich' will not be one of them," he wrote in a blog post Thursday.

Mr Gates, 69, said his eponymous foundation has already given $100bn (£75bn) towards health and development projects, and that he expects it will spend another $200bn, depending on markets and inflation, over the next two decades. In his blog post, Mr Gates cited a 1889 essay by tycoon Andrew Carnegie called The Gospel of Wealth, which argues that wealthy people have a duty to return their fortunes to society.

Mr Gates quoted Mr Carnegie, who wrote: "the man who dies thus rich dies disgraced." His latest pledge represents an acceleration in charitable giving. Initially he and his ex-wife Melinda had planned for the Gates Foundation to continue working for several decades after their deaths.

Giving away 99% of his fortune could still leave Mr Gates a billionaire – according to Bloomberg, the Microsoft founder is the fifth-richest person in the world.

In the post, he shared a timeline of his wealth that showed his current net worth at $108billion and a large hand-drawn arrow going down to close to zero in 2045. Mr Gates also said the foundation would draw from its endowment to give away $200 bn.

Along with Paul Allen, Mr Gates founded Microsoft in 1975, and the company became a dominant force in computer software and other tech industries. Mr Gates has gradually stepped back from the company this century, resigning as chief executive in 2000 and as chairman in 2014.

Mr Gates said he has been inspired to give away money by investor Warren Buffett and other philanthropists, however critics of his foundation say Mr Gates uses its charitable status to avoid tax and that it has undue influence over the global health system. In his blog post, he outlined three main goals for his foundation: eliminating preventable diseases which kill mothers and children; eliminating infectious diseases including malaria and measles; and eliminating poverty for hundreds of millions of people. (BBC/Reuters)