The St Andrews Agreement may come to be seen as a pivotal moment in Irish history, Northern Ireland Secretary Peter Hain has told the Commons.
Peter Hain hailed the St Andrews Agreement
Mr Hain said the NI parties face a choice between the St Andrews proposals and dissolution of the assembly.
He said the plan opens the way to a new dawn for democracy in Northern Ireland.
"A new democracy based for the very first time in NI's tangled history on the twin foundations of the rule of law and power sharing," Mr Hain said.
"These two foundations stand together or fall together: on the one hand, unequivocal support for the police and unequivocal support for the rule of law; on the other an absolute commitment by all the parties to share power in a restored Northern Ireland executive.
"Delivery on both these foundations was absent from the Good Friday Agreement; now it is in prospect."
Mr Hain said all parties must fully endorse the PSNI, actively encourage everyone in the community to co-operate fully with the police and play a full role in all the policing and justice institutions, including the Policing Board.
A new Programme for Government Committee will begin regular meetings at Stormont from Tuesday to agree priorities for the new Executive, he said.
However, Mr Hain also warned that if "something unravelled" between now and 24 November the Northern Ireland Assembly would be dissolved and the governments would revert to "plan B".
DUP leader Ian Paisley said his party had been promised that one of the foundations for a future devolved government would be full support for the police.
"We have the promise but we have not the delivery. I have made it clear before that if this is not delivered then we can not go forward," he said.
SDLP leader Mark Durkan said the DUP has moved "to the threshold" of accepting inclusive power-sharing and Sinn Fein to the threshold of accepting policing.
"Both parties, it seems, are at last honouring those key commitments of the Good Friday Agreement," Mr Durkan said.
Conservative Northern Ireland spokesman David Lidington congratulated the government and the leaders of the Northern Ireland parties "on what is clearly a major step forward".
"But we are absolutely clear that for this to happen, then Sinn Fein must deliver on policing," he said.
Earlier on Monday, Sinn Fein president Gerry Adams met Prime Minister Tony Blair in London.
It is thought the discussions touched on the shape of the economic package to accompany last week's St Andrews Agreement.
Sinn Fein and Ian Paisley's Democratic Unionists have until 10 November to respond to the proposed deal.
Sinn Fein leader Gerry Adams met Tony Blair in London
The roadmap to restore devolution to Northern Ireland was revealed with a deadline of 26 March 2007 for a new executive after talks in Scotland.
Republicans have called for a £1bn investment package to accompany a deal.
It is believed Treasury officials have already held discussions with their counterparts in the Irish Department of Finance about the package.
The Northern Ireland Assembly was suspended on 14 October 2002 amid allegations of a republican spy ring at Stormont.
The court case that followed collapsed and one of those charged, Denis Donaldson, later admitted working as a British agent.
Direct rule from London was restored in October 2002 and has been in place since.