Sinn Féin's chief negotiator Mr Martin McGuinness today insisted the Democratic Unionists needed to drop their demands for changes to power-sharing and cross-Border arrangements.
The Mid Ulster MP also said he believed it would be difficult to resolve all the issues blocking the return to devolution by tonight but insisted the negotiations were not yet bogged down.
"We would like to see this thing sorted out by today and are committed to trying to achieve that," he said.
"I don't think that is going to happen.
"That said, I think there is a dynamic in the process.
"I think as a result of the efforts made at Leeds Castle we now clearly see where the difficulties lie.
"The difficulties lie in the DUP's desire to change the fundamentals of the Agreement and I think the entire people of Ireland are looking to see who is going to defend the Agreement or who is going to assist the DUP.
"Sinn Féin is not going to assist in any way in bringing about any dilution or undermining of the Good Friday Agreement."
Mr McGuinness said proposals put forward by the British and Irish governments yesterday were unacceptable.
He also claimed that there were elements in the Northern Ireland Office who were working to undermine the 1998 accord.