Pro-life protesters march on US court

Tens of thousands of pro-life supporters have converged on the US Supreme Court to protest its landmark decision 40 years ago this week that legalised abortion in America.

Organisers of the annual March for Life on the National Mall in Washington on Friday expected a record crowd surpassing last year's turnout of 400,000, even with sub-freezing temperatures.

Cheering on the demonstrators from the Vatican was Pope Benedict XVI, who sent his best wishes via Twitter.

'I join all those marching for life from afar, and pray that political leaders will protect the unborn and promote a culture of life,' the pontiff tweeted on his Pontifex account.

Tuesday was the 40th anniversary of the Roe versus Wade decision in which the highest court in the land ruled that abortion was a strictly private matter between a woman and her doctor.

The 1973 decision is seen by the pro-choice camp as a breakthrough for women, but the pro-life movement - with support from the Roman Catholic and conservative Evangelical churches - sees itself as rapidly gaining ground.

'Being pro-life is the new normal... Americans are becoming more pro-life,' Jeanne Monahan, 40, the youthful new leader of March for Life after last year's death of its 88-year-old founder Nellie Gray, told the crowd.

In a Gallup poll last year, 50 per cent of respondents identified themselves as pro-life - in contrast to 41 per cent who were pro-choice, down from 56 per cent in 1995.