By Justin Webb
BBC correspondent in Washington
The US Senate has overwhelmingly passed legislation which makes it a separate offence to harm a foetus during an attack on a pregnant woman.
Opponents say the bill is the first step to giving foetuses distinct rights
Opponents bitterly denounced the measure as an attempt to strike at the legality of abortion.
The legislation is supported by President George W Bush, who will sign it into law, but opposed by his Democrat challenger, John Kerry.
It is likely to be a bitterly divisive issue in the presidential election.
Sponsors of this proposal said their only objective was to establish in criminal law that a foetus injured during an assault was just as much a victim of the crime as the expectant mother.
Opponents said they had no objection to increased penalties for attacks on pregnant women.
But the bill's definition of the foetus as "a member of the species homo sapiens at any stage of development who is carried in the womb" has horrified them.
Democratic Senator Dianne Feinstein said it was the first strike against all abortion in the US.
Although the economy and national security will loom large in the presidential election, so-called cultural issues like this one and that of gay marriage will also be of huge importance.
Here the Republicans believe they, not the Democrats, represent mainstream American opinion.