The DUP has said that it is getting impatient with the IRA over the issue of decommissioning.
Peter Robinson says the IRA needs to catch up
Deputy leader, Peter Robinson, said the IRA must make contact with General John de Chastelain to discuss putting its weapons beyond use.
The DUP has met the general twice in less than a week and Mr Robinson said the onus was on the IRA to provide details of decommissioning plans.
Mr Robinson said the IRA had to "catch up" with the process.
On Saturday, the DUP met General de Chastelain, head of the IICD (Independent International Commission on Decommissioning) for the second time.
It came after weeks of intensive negotiations between the British and Irish governments and the political parties Sinn Fein and the DUP.
They have centred on the responses from the parties to the proposals put forward aimed at restoring power-sharing in Northern Ireland.
The DUP has demanded photographic evidence of decommissioning as an essential part of any deal to restore devolution.
After Saturday's meeting, the DUP said it was unrealistic to set deadlines for a political deal when the IRA has still not met General de Chastelain.
Party leader Ian Paisley said it was "amazing" Prime Minister Tony Blair was setting deadlines for a deal when putting weapons beyond use had not been discussed with the IRA.
Mr Robinson told BBC Northern Ireland: "There has been a significant clearing of the table with other issues but the core and most important issue that is outstanding is decommissioning and that has to be resolved.
"It can't be resolved until the IRA catch up with the process and are prepared to get down to doing some work with General de Chastelain and his team to ensure that all the details of what is going to happen are known."
Sinn Fein President Gerry Adams has urged Mr Paisley to accept the proposals put forward by the British and Irish governments.
Mr Adams said both governments were very clear about Sinn Fein's position.
Mr Adams also appealed to republicans not to be provoked by the "unacceptable language" used by Mr Paisley.
Mr Adams said that comments by Mr Paisley, in which he said he would have to "swallow hard" to do business with republicans, were an acknowledgement of the prospect of Sinn Fein in government.
He said: "It is also the first begrudging, mixed-up, convoluted, angry acknowledgment by Ian Paisley of the Sinn Fein mandate. We shouldn't dismiss that.
"He also said in terms of getting a deal , it was 'now or never'. As far as we are concerned, it is now.
"He needs to come up to the plate and he needs to say 'yes'."