The divisions in Labour have been reinforced as members face deadline day in the party's leadership election.
A crunch meeting of the party's national executive committee (NEC) failed to reach consensus on how Labour's shadow cabinet should be formed, after nearly nine hours of discussion.
Deputy leader Tom Watson had put forward a plan for MPs to vote on membership of the shadow cabinet, a responsibility which currently rests with leader Jeremy Corbyn.
But Mr Corbyn has little support among Labour MPs, who overwhelmingly passed a vote of no confidence in him earlier this year.
He has instead suggested a system where party members would also have a say on shadow cabinet elections.
A motion from Mr Watson calling for a decision to be made before Saturday's leadership election result was defeated, by 16 votes to 15.
Mr Corbyn was among those to vote against it, but he did agree to further talks with Mr Watson and other senior Labour party figures.
They will then update the NEC at its next meeting, at the Labour Party conference in Liverpool on Saturday.
Mr Corbyn did not answer questions when members of the NEC finally emerged from the meeting at 8.30pm.
But Mr Watson and other senior figures in the party insisted the discussions had been positive.
Mr Watson said: "I'm very pleased. We had a very positive meeting.
"We have talks arranged to try and bring the PLP back together, reporting back to our national executive committee on Saturday."
Jon Trickett, NEC member and shadow business secretary, also called it "a very positive meeting".
He added: "We agreed to continue conversations. It's important that after this election for a new leader we reunite, because the Tories are doing awful things to our country and we intend to drive forward.
"It was a positive and productive conversation. The NEC meets on Saturday and we'll have further discussions at that point.
"Both sides of the argument felt we'd come to a better understanding of each other.
"It felt like it was a turning point for the whole party and I'm very confident now that we can reunite."
The ballot closes in the leadership race between Mr Corbyn and challenger Owen Smith at noon on Wednesday.
Mr Corbyn is widely expected to win the contest and has already vowed to "reach out" to fellow Labour MPs if re-elected.
Mr Smith has warned that Labour would be "decimated" if Mr Corbyn is re-elected.
In an open letter to party members and supporters, Mr Smith acknowledged the contest with Mr Corbyn has been "long and bruising" and that while many people did not want the challenge to take place, "the truth is it had to happen".
The Pontypridd MP then warned: "Our party is at a crossroads, and the choice we face is between renewing our party to pursue unity and power, or satisfying ourselves with ongoing division and opposition."
The NEC did agree two noteworthy changes to the party's processes. The Scottish and Welsh Labour parties will get to elect one member apiece to the NEC.
It was also agreed that all existing and new members sign a code of conduct about online behaviour or face being barred from the party.
The meeting also heard that Labour now has 551,000 members, reinforcing its position as the largest political party in Europe.