A deal will have to be done this month to restore Northern Ireland’s powersharing institutions, SDLP leader Colum Eastwood has said.
The summer unionist marching season and fresh focus on Brexit in the autumn could derail efforts to seek an accord later in the year, he said.
A preliminary meeting between the main Stormont parties and the British and Irish governments in Belfast lasted around 25 minutes but the pace is expected to be stepped up later this week.
Mr Eastwood said: “This will not get done if it goes beyond the end of this month. We can do it a lot sooner than that if people are up for it, but it needs to happen this month or I don’t think it will happen.
“We know from bitter experience what the summer can bring in Northern Ireland, we know the political difficulties that we are going to face in September and October. Now is the time to do it – we have no more excuses.”
Recommendations on transparency in government due to be made later this year following an inquiry into a botched green energy scheme will will “set the bar” for future standards, UUP leader Robin Swann said.
Powersharing collapsed two and a half years ago in a row between Sinn Fein and the DUP over the handling of the Renewable Heat Incentive (RHI) scheme.
Mr Swann said: “Unless it actually reaches what Sir Patrick Coghlin says needs to be done, if we set a bar that is actually lower than he sets, we are failing the accountability and transparency (standard) of what this place actually needs for full restoration of a functioning executive and assembly.”
DUP leader Arlene Foster said her party was “constructively engaging” in the talks and hoped they could quickly find a way forward.
“It has to be a balanced way forward and one that everyone in society can sign up to.”
Sinn Fein urged leaders to show political will despite the “improbable” circumstances.
Prime Minister Theresa May and Irish premier Leo Varadkar indicated an intensification of the negotiating process, which is led by the British and Irish governments.
Sinn Fein deputy leader Michelle O’Neill said: “It is very reasonable, the public deserve an assembly and executive, one that functions well, one that serves them well, one that looks after all in society.
“We are determined to try and achieve that, so what is required in this space is political will. We have political will, we are willing to discuss and to talk with the other parties.
“What we are asking for is absolutely reasonable previous agreements to be implemented, equality and respect for all citizens, integrity in government.”
Sinn Fein and the DUP are split over the place of the Irish language in society, abortion and the recognition of same-sex marriage.
Numerous rounds of negotiations have failed to secure a resurrection of the assembly.