First introduced by Ronald Reagan, the then Republican president, in 1984, it has been repealed by successive Democratic administrations and then reintroduced by the Republicans.

It has been called the "Mexico City policy" because it was unveiled at a United Nations conference there in 1984 as one of the main social policies of Reagan's administration.

Global concerns

The United States reportedly spends more than $400 million on overseas family planning assistance each year.

Critics of the ban said it deprived women of contraception and other vital health services in poor countries, leading to illegal "back alley" abortions and deaths.

The Center for Reproductive Rights says in nations such as Ethiopia and Lesotho, some non-governmental organisations are no longer able to offer comprehensive and integrated healthcare services to patients suffering from HIV/Aids.

Abortion rights opponents and groups who support the Mexico City Policy dispute this view, with Charmaine Yoest, the president of anti-abortion group Americans United for Life, telling Reuters that US taxpayers should not "bailout" the "abortion industry".

Obama's move comes only a few days after the anniversary of Roe versus Wade, the landmark 1973 US Supreme Court ruling that made abortions legal in the US.