Problems, but no crisis at Stormont: David Cameron
The prime minister has said he does not believe there is a political crisis in Northern Ireland.
David Cameron accepted that power-sharing at Stormont had problems.
But, in an interview with BBC NI, he said: "It is very difficult to make these devolved institutions work when you have parties that have been so opposed to each other in the past working together."
Sinn Fein MLA Gerry Kelly said on Wednesday power-sharing was in crisis.
Mr Cameron added: "I frankly think that the first minister and deputy first minister work hard at their relationship and they are doing the right thing by governing together."
He said he would not characterise the problems at Stormont as a crisis.
He said: "I wouldn't call it that but clearly there are a lot of difficulties to overcome."
Mr Kelly had described relations between First Minister Peter Robinson and Deputy First Minister Martin McGuinness as "not workmanlike".
Sinn Fein president Gerry Adams also said in the Dail (Irish parliament) that there was a lack of political leadership from Mr Robinson.
Mr Cameron accepted that making the executive and assembly work well was also going to be hard.
He also discussed the inter-party talks being chaired by the US diplomat Richard Haass, who is trying to find a political consensus over the past, parades and flags.
Pressed on whether he would intervene if agreement was not reached by the Christmas deadline, he said: "Let's let him do his work. Let us not assume these things are going to fail. Let us hope for success."
He added: "I will always try and do what I can to bring politicians in Northern Ireland together so that Northern Ireland can be a success story. Whatever that takes.
"I think Richard Haass is doing a good job, let's let him get on with it."
Asked if there was a point when he might consider intervening if the Haass talks failed, he said: "I don't want to start predicting that things are going to go wrong before they have had a chance to go right."
The prime minister also rejected criticism from the shadow Northern Ireland secretary Vernon Coaker who had claimed the government's approach to Northern Ireland was "semi-detached".
Mr Cameron said: "I don't accept that for a moment. I mean, after all, I am the prime minister that brought the G8 to Northern Ireland. I think Northern Ireland is an absolutely vital part of our United Kingdom and deserves real attention."
He added: "I brought together Martin McGuinness, Peter Robinson and the secretary of state here in Downing Street to sign a new accord for economic development in Northern Ireland so we can really get shared future going."
The prime minister's interview comes on the eve of the Conservative Party conference in Manchester.
One of the themes of this year's gathering will be that the people of England, Scotland, Wales and Northern Ireland are better off being part of the United Kingdom.
Asked how next year's Scottish referendum vote could impact on Northern Ireland, Mr Cameron said: "I hope there will be positive implications, because I hope Scotland will vote to stay in the United Kingdom and then we can start to take further steps to strengthen our United Kingdom and make sure everyone in our United Kingdom is proud to feel part of it."
He admitted that if the Scottish people voted to leave the union under his premiership he would be "desperately sad".
The referendum will take place on 18 September next year.
Hear David Cameron's interview on BBC Radio Ulster's Evening Extra from 17:00 BST, and on BBC Newsline on BBC 1 NI from 18:30 BST.