Some of the world's most powerful women, including US Secretary of State Hillary Clinton and Brazilian President Dilma Rousseff, have lamented the omission of women's reproductive rights in the Rio+20 summit's final statement.

Reproductive rights include a woman's right to decide the number, timing and spacing of children, the right to voluntarily marry and establish a family, as well as the right to the highest attainable standard of health.

The issue was a major bone of contention at the three-day UN summit on sustainable development, which was closing Friday with 191 UN members set to adopt a weak compromise statement on a roadmap to a green economy.

A reference to reproductive rights was included in the original summit draft, but it was dropped in the final version approved by negotiators Tuesday.

In her address to the summit Friday, Clinton insisted that "women are essential drivers of sustainable development."

"I applaud the bold call to action issued here in Rio by UN women and likewise the Rio+20 outcome document devotes a strong section to expanding opportunities for women," she said.

She welcomed the fact that the document "endorses sexual and reproductive health and universal access to family planning."

But she made clear that "to reach our goals on sustainable development, we also have to ensure women's reproductive rights."

"Women must be empowered to make decisions about whether and when to have children," the US chief diplomat said, adding that Washington would continue to work "to ensure that those rights are respected in international agreements."

"I would have liked to see the importance of reproductive rights acknowledged in the outcome from Rio+20," Danish Prime Minister Helle Thorning-Schmidt also said Friday in her own address to the summit.

On Thursday, Brazilian President Dilma Rousseff, the summit host, and other stateswomen also spoke in support of reproductive rights at a women's mini-summit on the sidelines of the Rio+20 conference.

"In Brazil, we are investing to overcome difficulties and precarity in access to public health services, with the full exercise of sexual and reproductive rights," said Rousseff, a 64-year-old former marxist guerilla.

Former Irish prime minister Mary Robinson, present at Rio+20 as a representative of "The Elders," a group of former leaders set up by South Africa's Nelson Mandela, meanwhile lashed out at the Vatican's opposition to reproductive rights.

"What do single men know about life, health and the decisions of poor women?" Robinson said in an interview with the Brazilian daily O Globo.

Cardinal Odilo Scherer, the Vatican's representative used his address to the summit to warn that the "promotion of a certain conception of health deeply threatens the dignity of the human person" and amounts to a "death sentence."

Several negotiators told AFP that opposition also came from many developing countries.

"It is scandalous that again a male-dominated gathering wants to dictate to women of the world how they control their bodies," said Kumi Naidoo, executive director of Greenpeace International.

"Rio+20 betrayed women," shouted several activists.

The summit's final document stresses the need to work "toward universal access to safe, effective, affordable and acceptable methods of family planning as this is essential for women's health and advancing gender equality."