French President Nicolas Sarkozy on Thursday demanded reforms of the United Nations and urged negotiations under a small group of countries to accelerate efforts to fight climate change.

Sarkozy, opening a one-day conference on deforestation, stood by the UN, saying there was "no alternative strategy" to a forum that gave all nations, rich and poor, a voice in a global arena.

But he said changes to the UN were way overdue.

"The UN is absolutely indispensable and yet at the same time, it's not working," said Sarkozy. "(...) I am certain that we need to reform the United Nations, otherwise the United Nations will end up in an impasse."

Reiterating previous ideas, Sarkozy proposed overhauling the Security Council, widening the number of members and apportioning seats on a regional basis.

But he reserved his main firepower for the flawed UN process on climate change.

Sarkozy blasted the Copenhagen summit last December as "an example of bad management."

Two years of talks failed to yield a hoped-for treaty on tackling carbon emissions blamed for disrupting the climate system.

More than 120 heads of state or government, arriving for the meeting's climax, were handed a draft text that Sarkozy likened to "volapuk," an invented 19th-century language translatable as "gobbledegook."

With fiasco looming, around two dozen countries haggled through the final night to craft a compromise and submitted it to the wider arena as a platform for action.

The so-called Copenhagen Accord would limit warming to two degrees Celsius (3.6 degrees Fahrenheit) but does not detail when or how this goal should be achieved nor commit signatories to binding pledges.

Sarkozy admitted the outcome was "frustrating" but argued that the rapid progress yielded by a small group in the space of a few concentrated hours was revealing.

It was time to ditch the format by which all issues are negotiated simultaneously by all countries under the 192-nation UN Framework Convention on Climate Change (UNFCCC), where unanimous approval is essential, Sarkozy said.

"These working methods have to change... who can believe that this can work?" he said, calling for a "representative" group of countries to do the essential haggling.

This should be the template for a renewed attempt at ministerial level in December, in the Mexican resort of Cancun, to build a post-2012 climate pact, he said.

Sarkozy threw his weight behind the UN's beleaguered climate scientists, under fire for flaws that have emerged in a landmark 2007 report, saying the panel "has earned the right to our gratitude."

"Climate change is a reality," he said.

The Paris conference gathered around 60 countries under a French-Norwegian initiative on helping deforestation, a major part of the climate-change problem.

Between 12-20 percent of carbon emissions come from loss of trees, which suck up carbon dioxide, and from conversion of forest land to agriculture.

One of the rare advances in Copenhagen was in how to offer rewards for poor tropical countries, making it worth their while to preserve forests rather than chop them down.

Progress was made in the UNFCCC negotiations on establishing principles of transparency, good governance and book-keeping that, in the future treaty, would unlock money for forest stewards.

Separately, six wealthy countries -- Australia, Britain, France, Japan, Norway and the United States -- agreed 3.5 billion dollars to help deforestation from 2010 and 2012.

The Paris conference, followed by a decision-making meeting in Oslo in May, focusses on how this money should be disbursed.

"We really do not have much time for many financial mechanisms to be established and so we hope that we shall be able to use the mechanisms that are already in place," Nobel Peace laureate Wangari Maathai told the meeting.