Delegates from more than 190 countries have struggled to break a deadlock on setting targets to preserve animals, plants and ecosystems, raising fears the two-week UN meeting might end in failure.
The biggest sticking point was a division between developing and industrial nations over working out a system to fairly share in genetic resources, such as medicine extracted from plants.
The UN Convention on Biodiversity meeting, held in Nagoya, south-west of Tokyo, has agreed on 16 of 20 strategic goals for 2020 but failed to reach consensus on the most contentious targets, including how much ocean space to set aside as protected.
Government ministers tried to hammer out final agreements and avoid the kind of collapse that befell last year's UN climate talks in Copenhagen.
"It's a race against the clock to get something agreed upon," said Nathalie Rey of Greenpeace International. "Everybody's saying we can't go home empty-handed. So there's real pressure to make this happen."
One of the conference's key goals is to set measurable targets that will slow or halt the rate of extinctions and damage to ecosystems from pollution, over-exploitation and habitat destruction.
Scientists warn that unless action is taken to prevent such biodiversity loss, extinctions will rise and the intricately interconnected natural world could collapse with devastating consequences, from plunging fish stocks to less access to clean water.
Decisions at the conference must be reached by consensus, meaning even one country can block agreements. And as is typical of such meetings, some countries strike deals with other nations, seeking progress in one area in exchange for their support in another.
Delegates were unable to agree on how much of the world's oceans to designate as protected, which could range from a marine sanctuary to areas where sustainable fishing is allowed. The draft text contained three figures - 6%, 10% and 20%.
Concerns about how to pay for executing such targets was also an obstacle.