The British Prime Minister David Cameron says it has not been possible to reach a deal with Northern Ireland politicians over the future of Stormont.

Mr Cameron and the Taoiseach Enda Kenny had presented a financial package and proposals to solve disputes threatening to destabilise the powersharing administration in Belfast in the early hours of Friday morning.

But they said it had not been possible to reach a deal overnight - though progress had been made and talks between political parties in Belfast are set to continue today.

Mr Cameron told reporters: "I think a deal is possible because the parties have done a lot of good work on the issues that need to be settled - the issue of how to manage parades, how to handle the past, the issue of flying flags."

"The real work that still needs to be done, I think, is to make sure the budget of the Northern Ireland executive is sustainable and works, so intensive work needs to be done between the parties on that issue and we stand ready to help - but what needs to happen is agreement."

He said he had put almost stg£1bn of investment for Northern Ireland on the table, if agreement could be reached on certain issues.

Mr Kenny said he also believed a deal was possible and the politicians "will be able to conclude the outstanding areas of disagreement on the matters that we have discussed".

Flanked by his DUP colleagues, Northern Ireland's First Minister Peter Robinson said he did not believe Mr Cameron had been "sufficiently challenged" by local politicians on his financial proposals.

He said: "We didn't do that because we had not ourselves been able to complete agreement on other aspects on the financial issues, namely the matter of welfare reform."

"I think the Prime Minister would have had more give in him if he had seen that that issue was going to be resolved."

Mr Robinson said he thought proposals developed by the Government were "an improvement" on those put forward by former US diplomat Richard Haass last year.

Northern Ireland's Deputy First Minister Martin McGuinness said the financial package on offer was "not credible" if Northern Ireland is to offset the impact of austerity measures.

Sinn Fein leader Gerry Adams was not impressed with the outcome, tweeting: "2 Govts exiting after most amateurish ham fisted episode I have ever been involved in."

2 Govts exiting after most amateurish ham fisted episode I have ever been involved in.

— Gerry Adams (@GerryAdamsSF) December 12, 2014

Speaking outside Stormont, Mr Adams says the governments must live up to their promises.

Speaking after the talks, the Tanaiste Joan Burton - who co-chaired discussions along with the Taoiseach, said: "While progress has been made over the last 24 hours, it is clear that the political parties need more time to consider the key issues of funding, welfare reform and dealing with the past."

"I believe the scope and potential is there to achieve a deal. But the complexity of the issues concerned and the implications of what has been proposed must be carefully examined in order to achieve a comprehensive agreement that successfully deals with all issues."

"We remain fully committed to the process and I have asked Minister of State Sean Sherlock to continue to work with Minister for Foreign Affairs, Charlie Flanagan, and officials from the Irish Government on making further progress," she added.