U.N. Secretary-General Ban Ki-moon and Danish conference hosts warned ministers on Tuesday to compromise at deadlocked global talks to salvage agreement on a new U.N. climate pact.

Ministers and negotiators from 193 countries struggled to make progress on core issues including emissions cuts and climate finance in the Copenhagen talks, three days before world leaders are meant to seal an accord.

"Three years of effort have come down to three days of action," Ban said. "Let us not falter in the home stretch." The U.N. process is meant to lead to a legally binding treaty next year.

"In these very hours we are balancing between success and failure," said Danish President of the two-week meeting, Connie Hedegaard, at the opening of the high-level phase of the talks. Organizers of the talks said environment ministers would work deep into night on Tuesday to narrow wide differences, saying the bulk of the work must be complete before more than 120 leaders formally joined the meeting on Thursday.