A District Health Board spokesperson is optimistic a new offer for nurses will be accepted.

DHB's have doubled their offer to nurses after the union threatened strike action this morning.

Members voted to take 48 hours of strike action, although that's subject to change depending on if they like today's last ditch pay offer.

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DHB spokesperson Helen Mason says they're now offering a package of more than half a billion dollars.

The offer will invest 520-million dollars between now and 2020 for base pay increases, more staff and improving work conditions.

"The difference between this offer and the last offer DHB made is an increase of about $250 million - so a quarter billion more funding has been put on the table for this offer to our nurses."

Mason says it would mean the salary of an experienced registered nurse will go up by more than $10,000 over a year and a half.

She says they made the offer to nurses this afternoon and hope they'll look at the proposal seriously.

"We would hope this will be well received - we see this as a significantly increased offer."

The nurses' union says it's reviewing the new offer.

Nurses Organisation Industrial Services Manager Cee Payne says they weren't expecting the offer to be publicised so soon.

She says the negotiation team will first pore over the offer... then they'll meet with the DHB delegates tomorrow.

Payne says they'll comment further once they've sent their full analysis of the offer to members on Thursday.