The United States is heading towards a demographic milestone: a 300 million population before the end of this year, rising from its current 298 million.

"This increase is largely a result of immigration, which accounts for four of every 10 people added to the United States every year," says Lawrence Smith Junior, president of the Washington-based Population Institute.

The United States is now the world's third most populous country, behind China (1.3 billion) and India (1.1 billion). Only two other industrialized countries appear among the world's 10 most populous countries: Russia (143 million people), in seventh place, and Japan (128 million), in tenth.

"By the middle of this century, the United States is projected to remain as the third most populous country with a population projected as high as 450 million, but it will be the only industrialised nation on the list of 10 most populous," Smith told IPS.