Governments are set to weaken pledges on boosting access to water and energy after a new draft negotiating text was issued at the Rio+20 meeting.
The text was issued by the Brazilian host government after it assumed leadership of the talks from the UN.
It affirms that nations must not slide back on prior pledges and names ending poverty as the "greatest challenge."
Brazil wants the text signed off before 130 heads of government and other ministers arrive on Wednesday.
The new text was not officially distributed to journalists, despite pledges that the meeting here was "accessible."
Preparatory talks were supposed to end on Friday evening, but at that stage only 37% of the UN's draft text had been agreed—which led to Brazil's decision to issue a revamped document.