US President Barack Obama has lifted a ban on federal funding for foreign family planning agencies that promote or give information about abortion.
The US is one of the biggest supporters of family planning programmes globally, but former president George W Bush blocked funds for abortion services.
Powerful anti-abortion groups in the US have criticised the lifting of the ban.
But aid agencies welcomed the move, saying it would promote women’s health, especially in developing countries.
A White House spokesman said Mr Obama signed the executive order without asking for coverage by the media late on Friday afternoon.
The issue of abortion services remains controversial in the US, pitting pro-life conservative groups against more liberal, pro-choice Americans who back a woman’s right to choose whether or not to have an abortion.
The BBC’s Richard Lister in Washington says this may be why President Obama signed the order with so little fanfare.
Organisations that had pressed Mr Obama to make the abortion-ban change were jubilant.
They called the funding ban the “gag rule” because it cuts funds to groups that advocate or lobby for the lifting of abortion restrictions.
The Planned Parenthood Federation of America hailed the president for “lifting the stranglehold on women’s health across the globe with the stroke of a pen.”
“No longer will health care providers be forced to choose between receiving family planning funding and restricting the health care services they provide to women,” the organization said in a statement.
But anti-abortion groups were quick to criticise the reversal of the funding ban.
“President Obama not long ago told the American people that he would support policies to reduce abortions, but today he is effectively guaranteeing more abortions by funding groups that promote abortion as a method of population control,” said Douglas Johnson, legislative director of the National Right to Life Committee.
A 1973 decision by the US Supreme Court legalised abortion.
A Gallup poll conducted last year showed that 54% of Americans think abortion should be allowed under certain circumstances, 28% believe it should be legal under any circumstances, while 17% back a total ban.
The policy has become a see-saw issue between Republican and Democratic administrations.
HAVE YOUR SAY I am personally opposed to abortion. However, as a US citizen, I would rather see uncensored information available to all Jim Nordblom, Mapleton, USA
Former President Bill Clinton, a Democrat, repealed the policy when he took office in 1993 and George W Bush reinstated it in 2001.
The ruling is also known as the Mexico City Policy, because it was first introduced at a UN conference there in 1984 by former Republican President Ronald Reagan.
In a move related to the lifting of the abortion rule, Mr Obama is also expected to restore funding to the UN Population Fund (UNFPA) in the next budget, the AP news agency reported.
The Bush administration contended that the fund’s work in China supported a Chinese family planning policy of coercive abortion and involuntary sterilisation, claims the UNFPA has vehemently denied.
In a separate move earlier on Friday, US regulators cleared the way for the world’s first study on human embryonic stem cell therapy.
While the decision of the US Food and Drug Administration is independent of White House control, Mr Obama is widely expected to adopt a more pragmatic and science-oriented approach to stem cell research.