The Supreme Court ruled in favour of abortion in 1973
The US Senate has voted to ban a form of late-term abortion, a decision which opponents say marks the start of a general assault on abortion rights.
It is the first legislative restriction to a woman's right to abortion since the US Supreme Court ruled in favour of the measure in 1973.
The bill outlawing the measure termed by abolitionists "partial-birth abortion" was passed by 65 votes to 32, with a number of Democrats joining in support.
Usually taking place during the fifth or sixth month of pregnancy, the procedure involves the extraction of the body of the foetus into the
vagina before the contents of the skull are suctioned and the intact
foetus is removed from the woman's body.
Many women who opt for "partial-birth" abortions do so because their foetuses have severe or fatal anomalies or because the pregnancy endangers their lives or health.
The bill will now go to the Republican-controlled House of Representatives, where it is expected to be approved soon.
President George W Bush, a committed Christian who is sympathetic towards the anti-abortion lobby, hailed the vote.
"Partial-birth abortion is an abhorrent procedure that offends human dignity, and I commend the Senate for passing legislation to ban it," he said in a prepared statement.
"Today's action is an important step toward building a culture of life in America."
The vote follows three days of emotionally-charged debate in which supporters of the bill attacked the procedure as barbaric, and opponents said the measure heralded a wider campaign against abortion.
The National Right to Life Committee said that many Americans don't understand how sweeping abortion rights actually are, and would favour more restrictions.
"The national debate over partial-birth abortion has educated people about how extreme our law is," Douglas Johnson said.
The legislation bans the destruction of the foetus when its head or a significant part of its body is outside of the mother, a rare procedure used in only a tiny proportion of abortions in America.
Republican Senator Rick Santorum called it an "evil, heinous procedure
that is outside the bounds of medicine."
But Democrat Barbara Boxer said that it was a political, not a medical term, and "a very emotional term ..for a procedure that is used in
situations where any other procedure might cause grave harm to the woman."
The legislation includes an exemption in cases where the procedure is necessary to save the life of the mother, but the exemption would not apply to a procedure to preserve her health or fertility.
Abortion rights supporters have pledged a court challenge, calling the measure unconstitutional.
"The Senate passed a law that they know is unconstitutional and endangers women's health," said Nancy Northup, president of
the Centre for Reproductive Rights, which has brought cases successfully challenging similar state laws.
Since the Supreme Court's 1973 Roe v Wade ruling allowed women the right to abortion, the pro-choice lobby has been able to count on enough support in Congress or the White House to see off challenges.
From 1995, abortion opponents have mainly focused their efforts on the "partial-birth" procedure, labelling it "infanticide".
Opponents of the ban - who say the term "partial-birth" is an emotive, politically-motivated description - argue that the procedure is rarely performed and that the ban could be extended to cover other forms of abortion.
Congress has passed legislation twice before to impose a ban, but then-President Bill Clinton vetoed both measures because they did not contain an exemption if the woman's health was at risk.
The Supreme Court is narrowly split on the issue of abortions, with 5 justices believed to be in favour, and 4 against.
Anti-abortion activists hope that President Bush will get the chance to appoint a sympathetic justice to swing the balance on the court during his term of office.