Arlene Foster is to give evidence today to the inquiry into the Cash for Ash scheme.
The mishandling of the renewable heat incentive led to the collapse of the Northern Executive, after the then Deputy First Minister Martin McGuinness resigned.
Talks on restoring power-sharing are due to resume this week, but DUP MP, Ian Paisley Jr, says his party will not "roll over" and give in to Sinn Féin's demands.
Mr Paisley Jr said: "We have always been open and up for any negotiation or any settlement that we can try to achieve that is fair and is balanced."
It comes after Mrs Foster yesterday confirmed she sought to keep a flawed green energy scheme in Northern Ireland open for several weeks.
The Renewable Heat Incentive (RHI) had been overspent and the decision was taken to close it as soon as "reasonably practicable", according to a witness statement from the DUP leader published by a public inquiry.
The minister in charge, Jonathan Bell, planned to close the scheme but it ran for a further fortnight after former First Minister Mrs Foster became involved.
She wrote: "Following the indication of a very early closure date representations were made by a number of public representatives that a little more time should be allowed before the scheme was closed.
"On this basis I asked the DETI minister to delay the closure by several weeks."
Mrs Foster had been enterprise minister when the scheme was established.
Power-sharing collapsed 15 months ago in a row over the DUP's handling of RHI.
Part of the problem with RHI was the failure to introduce cost controls, which were imposed on the scheme in Great Britain.
Mrs Foster wrote: "I had no influence whatsoever in relation to the cost controls introduced in 2015.
"However, in relation to the closure of the scheme in 2016 and with the agreement of the deputy First Minister, I suggested to the DETI Minister (Jonathan Bell) that the scheme should be closed as soon as reasonably practicable and certainly before the mid-March date that had been proposed."
Even after the First Minister requested a delay in closure it was still inside the original date proposed by the DETI minister.
She wrote: "I met with Minister Bell around this time in the presence of my special adviser Timothy Johnston.
"We discussed the need to allow a further two weeks for those with boiler installations in progress to complete the works."
She said she felt intimidated by Mr Bell's "aggressive" attitude at this meeting.
"Office of the First Minister and Deputy First Minister involvement in January and February 2016 regarding the timing of the closure of the scheme to new applicants was necessary and appropriate given the fact that the matter was by then cross-cutting."
The RHI ended up paying out more than it cost to fuel wood-burning boilers and led to the collapse of powersharing following a fall out between Sinn Féin and the DUP.
Earlier, Mrs Foster's former special adviser Andrew Crawford said he did not try to keep the scheme open.
He also said he thought minutes had been taken of a key meeting surrounding cost controls.
Mrs Foster and a senior civil servant have different recollections of a series of meetings on the issue while she was the powersharing minister responsible for RHI.
Mr Crawford said civil servants usually wrote in a blue book during discussions.
He added: "There were always people there who were taking notes.
"I cannot remember an occasion when they stopped recording those notes. I believed notes were always taken by officials."
- Digital Desk and PA