The 12 days of negotiations in the central Japanese city of Nagoya are aimed at securing agreement on how to stop the rapid loss of the world's plant and animal species, as well as their habitats.
However, after the first week, environment groups said the conference was becoming bogged down in the same kind of acrimony between developed and developing nations that have plagued UN climate change negotiations.
"What we need to see is a global alliance to protect life on earth but what we have seen so far are alarming divisions and a hardening of positions," WWF international director general Jim Leape said.
Under a best-case scenario, the negotiations would wrap up on Friday with a set of agreed targets for slowing the dramatic rate of biodiversity loss by 2020.
There would also be a deal on how developed countries would provide poor ones with funding to protect the world's natural habitats, plus an agreement on how to equitably share genetic resources.
However, the WWF and other environment groups monitoring the event said rich and poor nations were at loggerheads over many aspects of the potential agreement.
In one crucial stand-off, Brazil was insisting that no overarching deal could be reached unless there is agreement on how to share the benefits of genetic resources such as wild plants in forests that are used to make medicines.
Developing countries want an "equitable share" of the profits Western companies enjoy from the natural resources.
Greenpeace policy adviser Nathalie Rey, who is in Nagoya, said the talks were even going back wards in some areas.
"Previously negotiated texts have been reopened and unfortunately, key biodiversity protection targets for 2020 are being watered down or weakened," she wrote in a weekend summary of the talks.
"Everyone is saying that progress has been slow and painfully slow in some cases. If governments continue negotiating at this pace, there may be nothing on the plate by the end of the conference."
Nevertheless, there are still hopes the talks will pick up steam when environment ministers turn up in Nagoya this week and take over from their advisers for the final three days of the summit.
On the opening day of the talks last Monday, delegates from the 193 members of the UN's Convention on Biological Diversity (CBD) were told that a meaningful deal in Nagoya was crucial to save the world's biodiversity.