More than a hundred countries now support a French proposal to create a "World Environment Organisation" at the upcoming 20th anniversary conference of the Rio Summit, France's ecology minister said on Tuesday.

"More than 100 countries have now associated themselves with the proposal," Nathalie Kosciusko-Morizet said at a conference in Paris aimed at stimulating ideas for June 20-22 global gathering.

The idea is to beef up the UN Environment Programme (UNEP), which critics say lacks muscle for dealing with the world's worsening environmental crisis.

But rather than be just a branch of the UN, the proposed agency would help implement international environmental standards and include grassroots groups and business, according to the proposal.

Speaking afterwards to reporters, Kosciusko-Morizet said the United States "has yet to back" to the proposal, citing questions of sovereignty.

"However, we have already overcome the north-south divide in terms of numbers," she said.

Kosciusko-Morizet said the new agency was a key to the success of the "Rio+20" conference, designed to assess the two decades that have elapsed since the Rio Summit which nailed the environment to the political agenda.

It should be part of a rethink of the world's economy, in which green issues and social questions should be integrated into the search for profit, she said.

"The new capitalism which emerges from the crisis has to be environmental, or it won't be new," she said.

"We are looking for a new kind of environmental governance, something more inclusive, in which all parties have a stake and it's not just governments which have the right to speak."

She insisted on the word "World" in the organisation's name, saying it was an important nuance compared with "international," meaning an exclusive focus on nations.

The Paris conference gathered several hundred representatives from national and local government, thinktanks and civil society with the declared aim of gingering up a programme, called "draft zero," that is being hammered out for Rio.

According to a background document issued by the ecology ministry, countries that are supporting the French idea comprise more than 30 European countries and the 54 members of the African Union, as well as Thailand, Malaysia, Nepal, Chile and Uruguay.

Based in Nairobi, UNEP was set up in 1972 as an office of the UN, but as a "programme" it does not have the scope of an agency.

Its mission, according to its website, is "to provide leadership and encourage partnership in caring for the environment by inspiring, informing, and enabling nations and peoples to improve their quality of life without compromising that of future generations."

Many environmental experts believe UNEP is too underpowered for dealing with a crisis that now ranges from climate change and ozone depletion to overfishing, pollution and deforestation.