Julia Taft, assistant administrator of the UN Development Programme, said on Tuesday that Spain had estimated about $2 billion would be committed at the 23-24 October event.
Speaking to reporters after a meeting at UN headquarters Taft said 45 countries would pledge the “quite extraordinary” amount.
Earlier estimates had been that the international community would chip in as little as $1 billion in Madrid.
But the $2 billion is still well short of estimated needs.
Disagreements over launching the war on Iraq, followed by the US shutting the UN out of post-war administration has caused many countries to be reluctant about funding the reconstruction of Iraq.
Disagreements over waging war
still linger between the US and UN
To address those concerns, Taft said the World Bank and United Nations were putting the finishing touches this week to a new fund to be outside the control of Iraq's US-led administration, the Coalition Provisional Authority or CPA.
"It was agreed by a number of donors that they wanted to be helpful to the Iraqi people but they did not want to fund directly the Development Fund for Iraq, which is ... under the control of the CPA," Taft said.
"The donors asked us to come up with an alternative and we have been working with the bank to come up with a new Iraq Reconstruction Trust Fund which will have two major windows or pillars, one for the UN funds and programmes and one for the World Bank," she said.
The World Bank, the United Nations and the International Monetary Fund have estimated Iraqi reconstruction needs for 14 key sectors at about $36 billion over the period 2004-2007.
Their estimate does not include security, oil industry rehabilitation, illegal drug control, crime-fighting and cultural programmes, which are under the CPA's jurisdiction.