Brazilian negotiators have been accused of using strong-arm tactics at Rio+20 to secure a deal before heads of state start arriving for the Earth Summit later this week.

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

Brazil’s spokesman said on Monday he was optimistic a compromise text could be approved by Tuesday evening.

But frustrated delegates are now considering blocking the proposed text because of its lack of ambition and the “aggressive” tactics employed by the host nation.

“They are doing this more because of how they will look in the eyes of the heads of state and their desire to show a successful conference in the sense that it did not break down or that there was no outcome,” said the source. “If they carry on with these tactics the risk is that some delegations will feel they may need to block this because it is not ambitious enough.”

Luiz Alberto Figueiredo, the Brazilian foreign ministry spokesman said on Tuesday that consensus was close on proposals to strengthen Unep, manage the world’s oceans and establish sustainable development goals.

This appeared to mark progress after weeks of procedural wrangling and divisions between rich and developing nations, but the host’s tactics are now being questioned.

“They are speaking with two tongues; on the political level they say they want ambition and on the civil servants level they are being extremely aggressive in closing down the conversation,” said the source. “For the Brazilians, it is more important that the process is seen to be efficient rather than effective. The reality is that the Brazilians are around during the negotiations, then they go back to their room and they say they have taken all the comments and thoughts into account and then just produce their own text.”

The hosts denied bullying tactics. “The Brazilian role in the consultations has been praised by the UN and by virtually all countries. The developed countries also seem to be satisfied,” said a senior official.

Other delegates were more sympathetic to Brazil’s efforts to reach a compromise, saying the host had done its best to incorporate a wide range of views. But there was widespread frustration at the weakness of the compromise document and its lopsided emphasis on the economy above than the environment.

2012 Guardian News and Media Limited