The DUP has highlighted sticking points to a deal on the Troubles legacy issues in a letter sent to Northern Ireland Secretary Julian Smith.
They include examining whether all state-related killings should be investigated by a new body.
In her letter, party leader Arlene Foster details four areas she wants addressed in talks ahead of legislation being tabled at Westminster.
She writes “substantive discussions” are needed on the way forward.
As part of the deal which saw Stormont return, the government pledged, within 100 days, to introduce legislation to implement a legacy deal struck five years ago.
It includes an Historical Investigations Unit (HIU) to look into Troubles killings.
Mrs Foster’s letter, dated last week, states its caseload should not necessarily examine “all state-related deaths”.
It adds that concerns about the HIU “has led to many victims and survivors of terrorism losing confidence or not being supportive”.
It suggests victims could help “co-design” it and points out “over 90% of the deaths and injuries of the Troubles were caused by terrorist organisations”.
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Mrs Foster writes the idea the HIU could also investigate non-criminal police misconduct “is causing considerable angst”.
She also repeats the party wants a new definition of a victim to mean a person killed or injured through no fault of their own.
Speaking to Sky News on Sunday, Mrs Foster said “we need to revisit the Stormont House Agreement, because what is being proposed is not acceptable”.
“Victims were not treated well in the Belfast Agreement – that was left as an open wound.
“We now have been left, nearly 22 years later, and we’re still dealing with these issues.”
She said it was important to “recognise what actually happened here in Northern Ireland”.
“We did have a terrorist campaign and there were so many innocent victims as a result of that.”
Sinn Féin has long been calling for the introduction of the legacy deal struck in the December 2014 Stormont House Agreement.
Its MLA Gerry Kelly told the BBC programme The View last week: “All the work has been done.
“The agreement is there (from 2014). What we need is implementation.”