Activists both for and against abortion are staging rallies across the United States to mark the 30th anniversary of a Supreme Court decision legalising terminations.

Exactly three decades after the controversial Roe versus Wade decision, supporters of a woman's right to choose abortion are concerned that right may again be under threat.

US ABORTION FACTS

Abortion legalised by Supreme Court in landmark Roe v. Wade case in 1973 1.3 million abortions in 2000, down from 1.6 million in 1990 21.3 abortions per 1,000 women nationwide Number of providers fell from 2,042 in 1996 to 1,819 in 2000 33 states limit abortions for minors

President George W Bush praised the pro-life campaigners, saying they shared his commitment to build what he called "a culture of life" in the US.

Correspondents say debate on the issue has been more heated recently, with the largely-pro life Republicans in control of the White House and Congress.

But the six contenders for the Democratic candidature in the presidential elections next year all defend the right of choice for women.

Presidential support

The largest demonstrations took place in the capital Washington.

There thousands of anti-abortion demonstrators staged their annual "March for Life", starting at the Washington Memorial and ending at the Supreme Court.

Bush is staunchly pro-life

Many carried placards showing pictures of aborted foetuses or messages reading "Abortion is homicide".

"I'm here because 40 million babies are dead since 1973, and I want to be a voice for them," said Sara McKalips, a protester from Virginia.

Mr Bush addressed the crowd by telephone from St Louis, pledging to sign any bill banning the "abhorrent procedure" known by critics as "partial-birth abortion," a technique for late-term abortion.

Choice under threat

Many pro-abortion campaigners also took to the streets to voice their opinions and the National Organisation for Women (NOW) later planned to hold a candlelight vigil at the Supreme Court and other locations around the country.

The group's president, Kim Gandy, said it was to "remember the lives lost or destroyed by dangerous illegal abortion".

Pro-abortion campaigners are concerned about the Republican Party's strong anti-abortion faction, bolstered by the staunchly pro-life Mr Bush.

Norma McCorvey, the key figure in Roe v Wade, is now anti-abortion

Along with controlling the White House, the Republicans hold majorities in both houses of the Congress and a slim majority in the Supreme Court of 5-4.

"Thirty years of Roe and we're still fighting opponents of women's rights on this issue. But NOW activists nationwide are determined to ensure that abortion and birth control are safe, legal and accessible," Ms Gandy said.

Kate Michelman, president of Naral Pro-Choice America, says that if Mr Bush stays in office and the Republicans keep control of Congress, "American women will lose the right to choose by 2008".

Both sides claim that they have the support of the American people, but BBC News Online's Washington correspondent, Steve Schifferes, says polls show a majority of Americans still broadly support the right to abortion by a two-to-one majority.

Our correspondent says abortion is one of the most divisive issues in US politics.

Even the woman on whose behalf the Roe versus Wade case was originally fought, whose real name was Norma McCorvey, has subsequently come out against abortion, renouncing her pro-choice views in 1995 as a reborn Christian.