Brazil’s president, Dilma Rousseff, is under pressure to salvage some ambition from the Rio+20 Earth Summit as more than 150 world leaders and ministers fly in to criticism that the negotiations on global sustainability have already hit a “dead end”.

The mega-conference is billed as a “once-in-a-generation” opportunity to balance economic development and environmental protection, but a week of no-shows and low progress have prompted fears that it will end not with a bang, but a whimper of photo opportunities, handshakes and weak words.

Delegates have accused the organisers of using strongarm tactics to force through a weak text so that an agreement is in place before the start of a high-level segment on Wednesday.

The ghost of the Copenhagen talks – which ended with disappointment and recriminations – appears to be driving the attempt to force through an agreement, despite risks it could backfire spectacularly, said a senior source at the negotiations.

But while Copenhagen was riven by confusion and conflict, Rio+20 seems to be drifting in a sea of torpor and low ambition. In their bid to ensure a compromise deal is in place, NGOs say Brazil has watered down key proposals for GDP reform, valuing biodiversity, reducing poverty and moving the global economy on to a more sustainable track.

Barring a last-minute rejection by one of the main negotiating blocks, the draft that will be presented to the 100 leaders attending the summit will contain almost no timetables, definitions or ways to monitor new Sustainable Development Goals, nor will it strongly commit nations to move to a “Green Economy” that integrates environmental and social costs into decision-making.

Instead, civil society groups say the new text simply acknowledges the world’s dire environmental and social problems without spelling out how to deal with them.

2012 Guardian News and Media Limited