Image copyright Kelvin Boyes / Press Eye Image caption Sinn Féin said the talks have run their course

Sinn Féin has said the current phase of Northern Ireland inter-party discussions at Stormont Castle has run its course.

The party said it will not nominate its Stormont leader Michelle O'Neill as deputy first minister on Monday.

The decision means no power-sharing executive can be formed in time for Monday afternoon's formal deadline.

DUP leader Arlene Foster said to date "there was little to suggest that Sinn Fein want to secure agreement".

"The DUP stands ready to continue to discuss how we can secure new arrangements for Northern Ireland," she said.

The party did not attend today's session of talks as it does not negotiate on Sundays.

Sinn Féin's Mrs O'Neill said: "Today we have come to the end of the road.

"The talks process has run its course and Sinn Féin will not be nominating for the position of speaker or for the executive office tomorrow."

She said the party remained committed to making the power-sharing institutions work.

The parties have until 16:00 on Monday to resolve issues that divide them - if they fail, another snap Northern Ireland Assembly election could be called, just weeks after a poll held at the start of this month.

Northern Ireland has been without a functioning government since early January.

After the collapse of the power-sharing coalition between the Democratic Unionists and Sinn Fein, a snap election again returned them as the two largest parties. But Sinn Féin grew significantly, winning just one seat fewer than the DUP.

There was not much optimism that the relationship could be repaired in the three weeks allowed for talks.

'We will be back'

Sinn Féin leader Gerry Adams said: "We don't have the terms now to go forward and nominate for a speaker as Michelle has pointed out, or for a first, or a deputy first, minister.

"That's today. She also said, and I endorse this absolutely, that we do believe that we will have the conditions in the time ahead, because we want to be in the institutions."

He added: "Will we be back, will we get the institutions in place? Yes."

Earlier, Mr Adams criticised the DUP and the British government's approach to the talks.

Image caption The talks are being held at Stormont Castle

The DUP accused Sinn Féin of not being willing to attend roundtable sessions.

Former first minister Mrs Foster said: "While regrettable, the reality is that sufficient progress was not achieved in the time available to form a new executive.

"The DUP was ready to form a new administration without pre-conditions so as to allow us to have a budget and to deal with the many matters that currently face the people of Northern Ireland.

"Negotiations will only ever be successful when parties are prepared to be flexible in order to secure outcomes."

She added: "Throughout the course of Saturday, Sinn Féin behaved as if they were the only participants whose mandate mattered. This cannot and will not be the basis for a successful outcome."

Secretary of State James Brokenshire said that the people of Northern Ireland had voted overwhelmingly for devolved power sharing government.

"Even at this stage I urge political parties to agree to work to form an executive and provide people here with the strong and stable devolved government that they want," he said.

'Prolonged drift'

Tom Elliott of the Ulster Unionist Party said the current phase of talks was the worst he had been involved in.

"Unless there is a massive u-turn in terms of attitude from the two largest parties, then Northern Ireland could be in for a period of prolonged drift," he said.

"I understand the secretary of state took the attitude that the blockages to progress were devolved matters and therefore allowed the DUP and Sinn Féin to take the lead, with the government offering support.

"It looks like HM government will have to take the lead at 4pm tomorrow and that is a further indictment of the lead parties at Stormont."

Image copyright Pacemaker Image caption SDLP leader Colum Eastwood, with party colleague Nichola Mallon, said space was needed for fresh negotiations

SDLP leader Colum Eastwood said "rigid opposition to compromise on key issues, particularly from the DUP, has made a comprehensive resolution more difficult to reach".

He added: "Following talks over the last number of days it is clear now that an agreement will not be reached in the time left. That is a bitter disappointment.

"The secretary of state must immediately create space for all parties to refresh their outlook on the challenges we face and reach a positive accommodation that allows a restoration of power sharing."

'Constructive approach'

Speaking on the BBC's Sunday Politics, Alliance Party leader Naomi Long said if there is an agreement on Monday, much of it will have Alliance's fingerprints on it and that the party will continue to contribute to the talks over the next 24 hours.

"Whether we end up being in government or in opposition, we still want to facilitate government, we want it to happen," she said.

On Saturday Mrs Long said another election would be a vanity project.