UN Secretary General Ban Ki- moon on Tuesday called for a "fair, ambitious and comprehensive" deal on combating global warming at the Copenhagen climate talks and expected a legally binding treaty to be in place "as early as possible in 2010."

"Our goal is to lay the foundation for a legally binding climate treaty as early as possible in 2010," he said at the opening ceremony of the high level segment of the UN climate talks here.

"The stronger the agreement here in Copenhagen, the sooner it can be transformed into a legally binding treaty," he added.

Ban was speaking a day before world leaders arrive in Copenhagen to attend the UN Climate Change Conference.

Many countries are demanding a legally binding treaty to be reached in Copenhagen, but divisions between developed and developing nations, mainly over emission reduction and financing, were eroding chances of such a deal in Copenhagen.

"The time for delay and blame is over," Ban told reporters later.

He said a deadline must be set for turning any politically binding agreement reached at the Copenhagen talks into a legally binding treaty as soon as possible. "This deadline cannot be left hanging."

The UN chief called on negotiators to expedite the negotiating process and insisted the outcome from the Copenhagen talks should be "strong, robust and substantive."

"We are here to succeed," he said.