The Herald understands he will unveil detail on draft regulations for a future plain-packaging regime, such as what cigarette packages would look like.
Australia won the case against Philip Morris in December.
The WTO challenge is ongoing, but Mr Key has said he received advice late last year that the Government was on a "firm footing" to progress plain packaging because several other countries -- including the UK and Ireland -- had introduced it.
These countries did not face challenge under the WTO.
The Trans Pacific Partnership (TPP), signed on February 4, also allows tobacco control measures, so New Zealand could advance anti-smoking policies without risking a legal challenge.
A pack of 20 cigarettes will increase from about $20 now to around $30 in 2020 after hefty new excise increases were announced as part of last week's Budget.
The tax on tobacco will rise by 10 per cent on January 1 each year for the next four years.
That is expected to bring in an extra $425 million in tax over that period.
It will affect the some 15 per cent of adult New Zealanders who smoke each day - about 550,000 people.
That rate increases to 35 per cent for Maori, and 22 per cent for Pacific people.
