Finance Minister Grant Robertson has ruled out giving district health boards more funding so they can offer nurses a better pay deal.

A two-day strike is looming with nurses rejecting the latest offer, which Labour has described as the best they've had in more than a decade.

A strike notice has been issued for July 5, and another for July 12 is expected next week. But there remains a slim chance of a compromise, with the Nurses Organisation and the DHBs going into mediation.

"We hope by the end of Monday we might have another offer for members to consider," spokeswoman Cee Payne told The AM Show on Friday.

"We've always said it's not about money. This dispute's about safe patient care. It's about the value of nurses' work, and it's about having a quality nursing workforce in this country."

Mr Robertson said any new offer would have to be made using funds already allocated, as there's no more.

"We've said this is the offer that's on the table, if there's a way of organising it differently that's fine," he told The AM Show.

"This is the amount of money that's on the table and we're happy for discussions to go on, but we've been very clear in the last week about that."