Laci Peterson was pregnant

Women's groups say the campaign is a backdoor way of attacking the right of American women to abortion.

The body of Laci Peterson, who was pregnant with an unborn son she intended to call Connor, was washed up on the California coast earlier this year.

Soon after the bodies were discovered, Laci's husband Scott was arrested.

Under California state law he was charged not with one murder, but with two - the killing of his wife and unborn baby.

However, under US federal law the double charge could not be brought.

New act

It is just plain wrong that our federal government does absolutely nothing to criminalise violent acts against unborn children Senator Mike DeWine

Senator Mike DeWine is one of those pressing for this to be changed through the adoption of a Unborn Victims of Violence Act

He said: "It is just plain wrong that our federal government does absolutely nothing to criminalise violent acts against unborn children."

Opinion polls suggest such a measure would have overwhelming public support.

It is also backed by President George W Bush.

His spokesman Ari Fleischer said: "The president does believe that when an unborn child is injured or killed during the commission of a crime of violence the law should recognise what most people recognise, and that is that such a crime has two victims."

But supporters of abortion rights say the Laci Peterson case is being cynically used by pro-life campaigners to push through a law which significantly affects the abortion debate.

They say that if the federal government does recognise the foetus as an individual it erodes the legal basis for abortion.

Alternative agenda

The motivation is to eliminate reproductive freedom for American women Congresswoman Zoe Lofgren

Congresswoman Zoe Lofgren says severe punishments for attacks on pregnant women are fine - but recognition of the foetus is an agenda being pursued for other reasons.

"The motivation is to eliminate reproductive freedom for American women.

"It is not necessary to define a foetus as an individual person in order to punish someone who has inflicted harm on a woman and caused a miscarriage or foetal death."

However Doug Johnson, of the US National Right to Life Committee, said the case was nothing to do with abortion.

"Whoever killed Laci and Connor Peterson did not perform an abortion. This is a distinct issue in the law."

The bill is likely to pass.