When Bill and Melinda French Gates created the Gates Foundation in 2000, they had planned for the organisation to continue its work, using their remaining fortune, for several decades after they died.

But now, the billionaire Microsoft founder says he doesn’t want to wait that long to give away most of his wealth.

Gates announced on Thursday that he now plans to distribute “virtually all” of his wealth — around $US 200 billion ($312 billion), he estimates — within the next 20 years, before shuttering the foundation on December 31, 2045.

The announcement comes as President Donald Trump’s administration is working to slash funding for health, foreign aid and other public assistance programs — the types of causes the Gates Foundation supports — raising concerns about stalled progress on research and other crucial projects.

Gates wants to accelerate the foundation’s work on global health and equity initiatives and hopes the move will set a model for other billionaires, he said in a blog post published Thursday morning.

The pledge builds on Gates’ track record of promoting philanthropy.

He, along with ex-wife French Gates and Warren Buffett, launched the Giving Pledge in 2010 to encourage wealthy individuals to donate most of their fortunes to charitable causes either during their lifetimes or in their wills. It now has more than 240 signatories.

“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,” Gates, who turns 70 later this year, wrote.

“There are too many urgent problems to solve for me to hold onto resources that could be used to help people.”

The Gates Foundation, one of the world’s largest philanthropies, has already given away more than $US 100 billion ($156 billion) since its founding, including to develop new vaccines, diagnostic tools and treatment delivery mechanisms to fight disease around the world.

Gates has increased the pace of his giving in recent years, especially following the pandemic, but Thursday’s announcement marks a dramatic acceleration in the mobilisation of his wealth.

The Gates Foundation called it the “largest philanthropic commitment in modern history.”

Over the next 20 years, the Gates Foundation will focus on three main goals: ending preventable deaths of moms and babies, eradicating deadly infectious diseases and lifting hundreds of millions of people around the world out of poverty.

In its announcement, the foundation raised concerns about what it described as stagnant global health trends.

And in an interview with the Financial Times published Thursday, Gates accused fellow billionaire Elon Musk of “killing the world’s poorest children” because of his work at the Department of Government Efficiency cutting US international aid programs.

In an event in New York on Thursday announcing the commitment, Gates said he met with Trump in February to express his concerns, in particular, about cuts to USAID.

During that event — attended by billionaire Mike Bloomberg, singer Jon Batiste and other philanthropic partners — Gates Foundation CEO Mark Suzman said the world is in a moment “where we are facing, literally, the toughest political and economic headwinds to our agenda since we were established.”

He added that “much of (our) amazing progress is at risk.”

However, in his blog post Thursday, Gates expressed optimism that advancements in artificial intelligence, in combination with his giving, could increase the rate of progress.

Gates’ current net worth is $US 108 billion ($168 billion); Bloomberg’s Billionaires Index ranks him as the fifth wealthiest person in the world. Now, he said his net worth will fall 99 per cent by 2045.

The $US 200 billion ($312 billion) he expects to give away through the foundation over the next 20 years will come from its existing $US 77 billion ($120 billion) endowment and his personal wealth, including any earnings from ongoing business investments such as TerraPower, the nuclear power company he founded.

French Gates exited the Gates Foundation last year following the couple’s high-profile divorce in 2021.

She said in 2022 that she would not give away the bulk of her wealth through the Gates Foundation.

The announcement comes weeks after Microsoft, now worth more than $US 3 trillion ($4.7 trillion), marked 50 years since it was founded by Gates.

“It feels right that I celebrate the milestone by committing to give away the resources I earned through the company,” he wrote.