The United Nations says India looks set to overtake China as the world's most populous country.
In its latest report on population trends the UN says both nations will number 1.45 billion people in 2028.
Subsequently India's population will continue to grow until the middle of the century, while China's slowly declines.
The report also suggests the current global population of 7.2 billion will reach 9.6 billion by 2050, a faster rate of growth than previously estimated.
The population growth will be mainly in developing countries, particularly in Africa, the UN says.
The world's 49 least developed countries are projected to double in size from around 900 million people in 2013 to 1.8 billion in 2050, whereas the population of developed regions will remain largely unchanged.
The UN said the reason for the increase in its projection is largely new information on fertility levels in certain high birth rate countries.
The assessment of population trends is part of a series known as the World Population Prospects published every two years.