COPENHAGEN - All nations need to set tougher targets to combat global warming at a U.N. summit and the rich should spell out how much aid they will give the poor by 2020, U.N. Secretary-General Ban Ki-moon said on Wednesday.

We are just three days away from a final deal in Copenhagen. I am reasonably optimistic, Ban told Reuters Insider television on the sidelines of the December 7-18 meeting, which is seeking a new U.N. deal to combat global warming.

I have been urging both developed and developing countries that they should all come on board. I think that they can and must do more, in terms of mitigation (curbing emissions), in terms of financial support packages, he said.

Financial support for developing countries is one of the keys in getting this deal agreed in Copenhagen, he said.

He said the meeting needed to work out mechanisms for raising aid, a formula for sharing it and decide how much money can be provided -- that means size of financial support. These are keys. He said the amount was up to member states.

He denied a media report that he was conceding that the summit might not include promised financial aid for the poor.

The United Nations also wants countries to come up with $10 billion a year from 2010-12 as a quick start for a deal to help developing nations cope with global warming that will bring more floods, droughts, mudslides and rising sea levels.

That is a good start but this is just a start, he said of the $10 billion goal.