A fresh row over the failed Haass talks on flags, parades and dealing with the past has erupted, with UUP boss Mike Nesbitt warning of a further erosion of trust between the parties.
Mr McGuinness told question time: "We can be sure that the report from Richard Haass to the State Department and the White House will have been very accurate on how we found ourselves in a scenario that meant that we could not go forward with agreement from the five parties.
"The big challenge ahead is to continue to explore how we can conclude an agreement that will mean us all moving forward on the important issues of the past."
Mr Nesbitt told MLAs that any report back to the White House or US State Department by Dr Haass did not come with his authority.
Later he added that the First Minister had invited himself, the SDLP and Alliance to agree to ask Dr Haass to chair talks.
"It was agreed that the process would be between himself and his team and the five parties of the NI Executive, and no one else.
"At no point was I asked to give Dr Haass permission to make a report on the confidential discussions to any third parties.
"During question time today, Martin McGuinness made clear Dr Haass has reported to the State Department and the President.
"Who else is being briefed on the private discussions? These are key questions, if we are not to see a further erosion of trust and confidence in the parties at the heart of Government."