Published Tuesday, 19 January 2010
Mr McGuinness is holding separate discussions with Secretary of State Shaun Woodward and Irish Foreign Affairs Minister Micheal Martin.
DUP leaders are also to have top-level talks with government officials on Tuesday night after a further day of negotiations at Stormont.
Earlier both Sinn Fein and the DUP briefed representatives from the other political parties in the Assembly, in what was seen as a significant development.
The Ulster Unionists, the Alliance party and the SDLP met Peter Robinson and the DUP leadership, while Sinn Fein met the SDLP.
But Ulster Unionists warned they would not be "window dressing", as they joined the crunch talks.
"The suspicion is that it is a PR exercise", UUP MLA Basil McCrea told the media.
"We have made it clear to all parties that we're not there for window dressing. If there is not substantive engagement them the party will not be participating."
DUP environment minister Edwin Poots later played down rumours of trouble.
"I don't believe there is any particular wobble to the process," he said.
"Where we are at this point is we are narrowing down issues and those issues of concern will have to be resolved before all of the issues are resolved and ultimately we are working our way towards that."
Mr Poots also made clear that his party would not be bound by any Sinn Fein deadline.
"If there is to be a deal this week it will be a deal based on all the conditions being met, so we have always said we are not timebound, that we are condition-led."
UTV's Political Editor Ken Reid believes Wednesday will become "critical".
"We do get the feeling that we're at quite a delicate stage", he said.