White people will no longer make up a majority of Americans by 2042, according to new U.S. government projections. That's eight years sooner than previous estimates, made in 2004.

The U.S. has been growing more diverse for decades, but the process has sped up through immigration and higher birth rates among minority residents, especially Hispanics. The country is also growing older.

"The white population is older and very much centered around the aging baby boomers who are well past their high fertility years," said William Frey, a demographer at the Brookings Institution, a Washington think tank.

"The future of America is epitomized by the young people today. They are basically the melting pot we are going to see in the future."

The Census Bureau on Thursday released population projections through 2050, based on rates for births, deaths and immigration. They are subject to big revisions, depending on immigration policy, cultural changes and natural or manmade disasters.

The U.S. has almost 305 million people today. The population is projected to reach 400 million in 2039 and 439 million in 2050.

Hispanics to double by 2050

That's like adding all the people from France and Britain, said Steve A. Camarota, director of research at the Center for Immigration Studies, a Washington group that advocates tighter immigration policies.

White non-Hispanics make up about two-thirds of the population, but only 55 per cent of those younger than five.

By 2050, whites will make up 46 per cent of the population and blacks will make up 15 percent, a relatively small increase from today. Hispanics, who make up about 15 per cent of the population today, will account for 30 per cent in 2050, according to the new projections.

Asians, which make up about five per cent of the population, are projected to increase to nine per cent by 2050.

The population 85 and older is projected to more than triple by 2050, to 19 million.