UN Secretary-General Ban Ki- moon Monday voiced confidence for an agreement next month on fighting global warming even as key issues remain unresolved, a day before he travels to Washington D.C. to discuss with senior officials and congressional leaders what world governments expect in terms of the U.S. role.

"The secretary-general is confident that governments will reach agreement in Copenhagen on the fundamental issues that will form the substance of a legally binding international agreement which is the end goal for guiding action on climate change," the director of the UN secretary-general's Climate Change Support Team, Janos Pasztor, told a news conference at the UN Headquarters in New York on the upcoming summit in the Danish capital of Copenhagen.

Although in all likelihood it will not be possible to complete all the work needed for a legally binding agreement at Copenhagen, he said, the meeting should make clear what needs to be done in the three core fundamental issues that remain unresolved -- ambitious mitigation targets in the developed countries, how to consider mitigation actions in developing countries, and financing.

"Those are the three key issues where there still needs to be agreement, and they are precisely the issues where heads of state and heads of government need to be engaged because those issues are so important for the overall economic development of the countries that you cannot expect the negotiators themselves to make a move," he added.

Asked why, in that case, Ban was confident, he replied "Because they can be resolved, that's why." That confidence is based on his recent conversations with world leaders in which everyone wants to have a deal in Copenhagen, Pasztor said.

"There is tremendous interest and while we're not quite there yet, the willingness is there to make it happen, so it is not a question of whether or not we're going to have a deal, it's a question of how we're going to make sure that we get a good deal in Copenhagen and the secretary-general is convinced that it is possible and therefore it will happen," he said.

World governments are seeking to agree to a successor to the Kyoto Protocol, the 1997 treaty that committed 37 industrialized states to cutting emissions by an average of 5 percent against 1990 levels over the period from 2008 to 2012.

On Friday, as the last preliminary negotiations before Copenhagen wrapped up in the Spanish city of Barcelona, Yvo de Boer, executive secretary of the UN Framework Convention on Climate Change (UNFCCC), said developed countries would need to provide at least 10 billion U.S. dollars to enable developing countries to immediately develop low-emission growth and adaptation strategies and to build internal capacity.