He told French BFMTV he would present a new compromise text of a deal to combat global warming on Saturday morning, aiming for an accord among almost 200 nations at around midday, not on Friday as originally planned, Reuters reported.
"But the atmosphere is good, things are positive, things are going in the right direction," he said. The annual UN climate meetings frequently stretch into the weekend.
The talks, which began on Nov. 29, had been due to end on Friday.
"The night (into Friday) was very hard," one source said.
The talks held overnight revealed continued disputes over issues such as how to balance actions by rich and poor to limit greenhouse gases and also the long-term goals of any agreement to limit emissions, sources said.
Separately, China's President Xi Jinping and US President Barack Obama spoke by telephone and said their countries would maintain cooperation on climate change, Chinese state television reported.
Late on Thursday, Fabius unveiled a slightly trimmed 27-page draft text that removed some main points of contention.