Northern Ireland's First Minister Peter Robinson has demanded changes to Richard Haass's proposals to deal with a number of controversial issues in the peace process.
Mr Robinson was speaking after reviewing the draft document drawn up by Dr Haass and the vice-chair of the talks, Meghan O'Sullivan.
The DUP leader said he could not agree to any of the papers on the talks table and claimed matters seemed to be moving backwards on flags.
"Nobody is throwing the towel in at this stage. We are just saying that there is not a set of proposals that we can support, agree to or recommend," he said.
Mr Haass, a former US diplomat, is in London today to meet Northern Ireland Secretary Theresa Villiers ahead of further five-party talks later this week.
But it was clear Mr Robinson was unhappy with proposals put before his party, Sinn Féin, the SDLP, the Ulster Unionist Party and the Alliance Party,
"There are some things that are totally unacceptable and we would be outraged if we really believed that Dr Haass was serious in believing that that was going to be an outcome," he said.
"I suspect that Dr Haass, like everybody else, is hearing views from a wide range of people and putting some of their comments within the papers to allow people to react, well, he is going to get a reaction."
Mr Robinson said some of the experienced foreign policy expert's suggestions were still unacceptable to the DUP and very considerable work had still to be done to mend the "inadequacies".
Parades, the flying of flags and the legacy of the Troubles are issues that were not resolved by the peace process or the Good Friday Agreement.
Mr Haass, a former envoy to Northern Ireland during the Bush administration, has spent weeks in discussions in Belfast, London and Dublin after he was enlisted to submit recommendations to the ministerial Executive at Stormont.
Mr Robinson did not disclose details of the negotiations, but claimed they had gone backwards on flags. He said hopes for progress on all issues remained.
"If I thought that was the final paper there would be steam coming out of my ears," he added.
"But it is not the final paper and we still have work to do and we are up to doing that work."
Sinn Fein Deputy First Minister Martin McGuinness took to Twitter to issue his response.
"Let's prevent the paint lifting off the wall. The more excitable amongst us should cool their jets," he said.
Tomorrow, the political parties will meet the US negotiating team separately.
Wednesday and Thursday have been set aside for round-table discussions involving all the parties.
The hope is that an outline agreement might be reached by the weekend.
Dr Haass has said his target is to make meaningful progress before the Christmas holidays.