The Latest: UN chief: 'Optimistic' on ambitious climate deal

U.N. Secretary-General Ban Ki-moon says he is "reasonably optimistic" that countries will reach a strong agreement to slow global warming at Paris talks scheduled to finish Friday.

The last global accord on global warming, the 1997 Kyoto Protocol, only required rich countries to cut emissions.

Activists have a new way of trying to increase pressure on negotiators at the Paris climate talks — with caricatures of big-headed world leaders and piped-in voices from people around the world who want a robust agreement to fight global warming.

A cacophony of languages and pleas resonated in an effort to remind negotiators of concerns of people from countries vulnerable to rising seas and increasingly extreme weather caused in part by man-made carbon emissions.

Many activist groups want the Paris accord to call for an end to fossil fuel use in the long term and to back firm pledges by rich countries to help poor countries pay for future damages caused by climate change.

U.S. Secretary of State John Kerry is meeting with the environment ministers of two of the largest developing nations as negotiators try to hammer out details of a global accord on climate change by the end of the week.

Diplomats and climate negotiators worked almost until dawn and have now resumed talks, narrowing down options in a 29-page draft of a global accord to tackle climate change a day before a self-imposed deadline for the unprecedented agreement.