UNITED NATIONS, Feb. 17 (Xinhuanet) -- The world's population has reached 6.5 billion in 2005, a billion more than 1993, despite lowfertility in developed countries and high mortality in developing countries, a new United Nations report said on Thursday.

    The report, released by the UN Economic and Social Council, estimated that the world's population could reach 7 billion in 2012 and could stabilize at 9 billion in 2050. The rate of growth has fallen, however, to 1.2 percent now from 2 percent in the late1960s.

    The report, covering population size and growth, urbanization and city growth, population aging, fertility and contraception, mortality and international migration, was released in advance of the next session in April of the 47-member UN Commission on Population and Development.

    "Most developed countries exhibit fertility levels at or below the replacement level. Although most developing countries are far advanced in the transition from high to low fertility, some developing countries, mainly in Africa, still exhibit high fertility," the report said.

    In the last century, "mortality experienced the most rapid decline in the history of humanity, owing to better hygiene, improved nutrition and medical practices based on scientific evidence," it said. In Africa, however, HIV/AIDS has markedly increased mortality.

    Presenting both opportunities and challenges in this century, the report noted, "the current population picture is one of dynamic population change, reflected in new and diverse patterns of childbearing, mortality, migration, urbanization and aging."