SAN FRANCISCO, Sept. 18 (Xinhua) -- U.S. billionaire Bill Gates on Tuesday called for greater investment in the fight against global poverty, which he warned of "on the verge of stalling."

In a letter included in the annual Goalkeepers 2018 Data Report released Tuesday by the Bill and Melinda Gates Foundation, Gates, principal founder of Microsoft Corporation and philanthropist, said that "decades of stunning progress in the fight against poverty and disease may be on the verge of stalling."

In partnership with the University of Washington's Institute for Health Metrics and Evaluation, the foundation made a detailed analysis of 18 key metrics of quality of life in countries around the world.

According to its statistics, the number of people living below the extreme poverty line across the globe has fallen from 36 percent to 9 percent since 1990, but demographic trends on worldwide scale show that progress toward poverty relief could be stalling.

"This is because the poorest parts of the world are growing faster than everywhere else; more babies are being born in the places where it's hardest to lead a healthy and productive life," Gates said.

"If current trends continue, the number of poor people in the world will stop falling - and could even start to rise," he added.

Since 2000, more than a billion people have lifted themselves out of the extreme poverty, and the progress made by China and India contributed to the overall success in poverty relief, he said.

However, Gates said the geography of poverty is changing in that extreme poverty is becoming heavily concentrated in sub-Saharan African countries, where 86 percent of the extremely poor people in the world are projected to live by 2050.

The world's priority for the next three decades should be a third wave of poverty reduction in Africa, which was preceded by the first wave in China and the second in India, he said, noting that African will have to face a huge challenge in eliminating poverty as the population on the continent will nearly double in size by 2050.

The Gates Foundation, established in 2008 and headquartered in Seattle, Washington state on the U.S. west coast, urged world governments to make strategic investments in health care and education to help poverty-stricken countries.

"The conclusion is clear: to continue improving the human condition, our task now is to help create opportunities in Africa's fastest-growing, poorest countries," he said.

The foundation's 2018 report aims to confront pressing yet neglected challenges and track progress toward collective goals such as cutting childhood mortality, more investment in youth health and education, as well as financial participation and access to family planning resources.