The latest report from the Independent Monitoring Commission is expected to be "very significant", the prime minister's official spokesman has said.
What the report says about the IRA will be examined
He said it will provide the "definitive answer" to questions about the IRA campaign in all its forms being over.
The IMC, which monitors the IRA and loyalist ceasefires, has given its 12th report to the UK and Irish governments.
The report will form the basis of talks in Scotland next week for talks aimed at restoring devolution.
It is to be made public on Wednesday and Tony Blair's spokesman said that the report will determine whether Sinn Fein is living up to its commitment in word and deed to use only political means.
BBC Northern Ireland's home affairs correspondent Vincent Kearney said most of the attention will be focussed on what the report says about the IRA.
"The commission is expected to expand on its comments last month when it said the IRA's command and control structures were still intact - but that this might be necessary to manage the change from violence to politics," he said.
"The DUP has met the commission since that statement and is demanding clarification about the current structure and activities of the IRA.
"The party also wants to hear what the IMC has to say about the murder of self-confessed British spy Denis Donaldson at his holiday home in Donegal in April.
"The report will also contain an assessment of the activities of loyalist paramilitary groups, and republican dissidents.
"But with the governments stepping up the pressure for a political deal, most attention will focus on what is said about the IRA."
The Independent Monitoring Commission was set up by the British and Irish governments in January 2004.
Most of its reports have concentrated on activity by paramilitary groups in Northern Ireland.
However, it also monitors the "normalisation" of security measures in the province.
Its four commissioners come from Northern Ireland, the Republic of Ireland, Britain and the US.