Ulster Unionist leader Mr David Trimble will block any restoration of the power-sharing Executive in the absence of an IRA declaration that its terrorist campaign is over.
Mr Trimble said the British government must also explain how the Assembly will function once it is elected.
He told BBC Radio 4's Todayprogramme: "The big question is whether the institutions can be reinstated." He said the British government had been working very hard on this, "but I have to say, as the way things stand at the moment, they have not succeeded.
"They need to think very carefully now about what they do. They [people in Northern Ireland] looked at the Gerry Adams statement and they found very little meaning in it at all.
"The government may want to talk it up but it's a long way short of the solution to the problem that led to suspension. The government is going to find itself running out of road very quickly," he said.
PA