Negotiations to restore power-sharing in Northern Ireland will be allowed to extend until Monday, despite Stormont parties missing today's statutory deadline to reach agreement.

Downing Street said Northern Ireland Secretary James Brokenshire will make a statement on Monday outlining the UK government's intentions.

A Downing Street spokesperson said the passing of today's 4pm deadline "does not mean the efforts to restore the executive are ending".

Alliance Party leader Naomi Long earlier said Mr Brokenshire had told the parties he would "reflect" over the weekend on how to proceed, and allow further talks to go ahead in the interim.

She said she was "extremely frustrated and disappointed" that the latest deadline would not be met.

The key sticking point in the way of a deal has emerged as Sinn Féin's demands for an Irish Language Act, which would bestow official protection for Irish speakers.

The DUP is willing to legislate on the language issue, but only if Ulster Scots speakers are included in any Act, a condition Sinn Féin has rejected.

Ms Long said: "This Assembly has often been criticised and held in low esteem.

"We do ourselves no favours when we continue to let deadline after deadline slip."

She said it was inexcusable that a row over the "name" of an Irish Language Act was halting progress.

"That is ludicrous after six months of negotiation and debate on the issue," she said.

Colum Eastwood of the SDLP said political leaders need to show courage to seal a deal to restore power-sharing.

Mr Eastwood said he was encouraged that some progress had been made.

"Political leaders now need to be challenged to show some courage and get this across the line.

"There is too much at stake to allow our institutions to fall - the deadline may have passed but we still need to get the deal done.

"We cannot allow Northern politics to fall into a permanent status quo of huge frustration."

Ulster Unionist leader Robin Swann said: "Today's events are extremely disappointing. It's not what we wanted and it's not what the people of Northern Ireland wanted. I believe that the majority of people voted at the last Assembly election for local politicians to take local decisions.

"Everyone should recognise that if a functioning Executive and Assembly are not in place and we go to direct rule, then they should not expect either to be back in place any time soon.

It is the height of folly to allow any of the participants to hold a veto over the formation of the devolved institutions

Earlier, Minister for Foreign Affairs Simon Coveney said significant progress had been made and "gaps are to be bridged" on some issues, but he believed an agreement is possible.

He added that all parties are committed and convinced that devolution is the best way to deliver for Northern Ireland. 

Speaking alongside Mr Coveney, Mr Brokenshire said the parties are continuing to engage intensively with a view to forming an executive.

He also said much progress has been made, but that a number of issues remained outstanding.

He said the UK government will work with the parties toward their "critical objective" of forming an executive, but that he has made clear to party leaders that it is for them to reach an agreement that will pave the way for this.

Mr Brokenshire has said previously failure to reach a deal would have "profound and serious" implications.

The institutions imploded in January when DUP leader Arlene Foster was forced from office after Sinn Féin's then deputy first minister, the late Martin McGuinness, quit in protest at the DUP's handling of the Renewable Heat Incentive - a scheme that left the administration facing a £490 million overspend.

His move triggered a snap Assembly election in March.

A number of attempts to restore power-sharing between the five main parties following that poll floundered, with three UK government deadlines for a deal having already been missed.

Green Party NI leader Steven Agnew claimed the logjam essentially boiled down to the name of potential legislation that would protect Irish language rights.

Mr Agnew, who is not directly involved in the talks at Stormont but did attend the whips' meeting, said: "We seem to be arguing about the name on the face of a piece of legislation.

"It's about parties saving face, rather than parties trying to save the Assembly. And I think that's wrong and we should give the institutions the respect they deserve."

British Prime Minister Theresa May's official spokesman said: "If, despite our collective efforts, it proves impossible to re-establish the executive, we will need to consider the options to ensure Northern Ireland has the political stability that it needs.

"In terms of what those options are, I wouldn't get into that at this stage."

Meanwhile, there was one political delivery on deadline day in Northern Ireland.

While the negotiations stalled at Stormont, SDLP leader Colum Eastwood was in a maternity unit witnessing the birth of his second child.

Mr Eastwood and wife Rachael have welcomed daughter Maya Olive into their family.

With the 34-year-old leader otherwise indisposed, SDLP Assembly member Nichola Mallon delivered the party's media response to developments at Stormont.

 Mr Eastwood took to Twitter to share his good news.