By Steven Duke
Editor, One Planet
Mr De Boer will lead the climate change negotiations
The UN's top climate official has said that the richest nations will have to put $10bn "on the table" during the Copenhagen climate change summit.
Yvo De Boer, who will lead the negotiations, said such a commitment was necessary for their success.
He insisted the burden of climate change must be shared and that the money would help developing countries.
Leading nations participating in the summit must, he said, sign an agreement to reduce greenhouse gas emissions.
Mr De Boer, head of the United Nations Framework Convention on Climate Change (UNFCCC), said the $10bn (£6bn) pledge would be "a good beginning".
"(It) will allow developing countries to begin preparing national plans to limit their own emissions, and to adapt to climate change," he told the BBC World Service's One Planet programme.
Mr De Boer was less keen to put an exact figure on the levels of emission cuts the biggest economies should commit to.
Some scientists have called for a 25-40% reduction by 2020 - a proposal he describes as "a good beacon to be working towards".
As well as the hard cash and paper pledge from developed nations, success at Copenhagen will come from one other factor, he revealed.
"If on that piece of paper, China, India, Brazil and other major developing countries have offered national actions, that will significantly take their emissions below business as usual... that for me will be a success."
China leads way
Nations will be asked to take emissions below "business as usual"
Mr De Boer, who helped negotiate the Kyoto Protocol on tackling greenhouse gases in 1997, admitted the recent financial turmoil had made his job more difficult as governments focus on "budget deficits and the banks they've just bailed out".
But he praised some countries for seeking to turn the troubles to their - and the environment's - advantage.
"A number of countries - with China and Korea in the lead - are seeing this economic crisis as an opportunity to turn a corner.
"Those countries are in a serious way making investments in renewable sources of energy; modernising their power sector; coming up with different types of vehicles that are more geared towards tomorrow's needs than yesterday's."
Despite his belief that some countries are seeing the economic potential of tackling climate change, Mr De Boer said he recognised that getting 192 nations - from Afghanistan to Zimbabwe - to agree on the issue was "a bit like herding cats".
"You can take one of two approaches, you can either try and herd them from behind with a stick, which generally has them shooting off in different directions, or you can walk in front holding a tasty fish and that will get them to follow you more willingly," he said.
You can hear the full interview with Yvo De Boer on the 23 July edition of the One Planet programme on the BBC World Service.