China will lift more than 10 million poor people living in rural areas out of poverty in 2018 and help relocate a further 2.8 million now in impoverished regions.
Cairo, Mumbai, Beijing and Dhaka are all closing in on the 20-million inhabitant mark. It said that after surging past Tokyo in 2028, the population of Delhi urban agglomeration would grow to 39 million by 2030 from 29 million now.
Currently, 55 per cent of the world's population lives in urban areas. The Guardian reports that now, 55 percent of the world's population resides in urban areas and this will increase to about 68 percent in 32 years.
Two of India's cities are among the world's largest.
The UN study, carried out by the world body's Population Division, predicts that Tokyo's population will start to decline in the coming two years and that it will be surpassed as the world's largest city by New Delhi towards 2028. India, China and Nigeria will account for more than a third of that expansion.
The population decline will be the highest in villages, the report says.
This increased pressure is giving rise to so-called megacities - those with more than 10 million inhabitants.
Currently, Asia is home to 54 percent of the world's urban population, though levels of urbanization are considered to be low in the region.
The world's rural population will peak in a few years then decline by 2050, according to the report by the UN's population division.
The growth is caused by an accelerating shift from rural to urban living across the world, particularly in Asia, which despite hosting some of the world's largest cities has lagged behind other parts of the world in terms of overall urbanization.
"When urban growth is rapid, ensuring access to housing, water, sanitation, electricity, public transport, education and health care for all is especially challenging", John Wilmoth, director of the Population Division, said at a United Nations news conference, according to Reuters.
To ensure that the benefits of urbanization are fully shared and inclusive, policies to manage urban growth need to ensure access to infrastructure and social services for all, focusing on the needs of the urban poor and other vulnerable groups for housing, education, health care, decent work and a safe environment.
As the world continues to urbanize, sustainable development depends increasingly on the successful management of urban growth, especially in low-income and lower-middle-income countries where the pace of urbanization is projected to be the fastest.
The News Agency of Nigeria (NAN) reports that DESA in earlier report said: "By 2050, the third most populous country will be Nigeria, which now ranks seventh, and which is poised to replace the United States".