Top epidemiologist Michael Baker says New Zealand is not ready to move to level 2 and his advice to the Prime Minister is to "pause for a few more days".

Ministers meet at 10.30 this morning for an extended Cabinet meeting to discuss the move out of level 3, and Prime Minister Jacinda Ardern will announce the decision at 4pm.

It will be broadcast live on nzherald.co.nz and Newstalk ZB.

Today's decision could see New Zealand move into level 2 as early as Wednesday.

But Baker, a professor of public health at the University of Otago Wellington, told Newstalk ZB's Mike Hosking this morning he would prefer to wait a little longer than that to ensure the public was fully on board with the requirements of level 2.

Under level 2 rules, people can pop their bubbles to see loved ones, visit bars and cafes, go shopping and travel domestically. Gatherings of fewer than 100 people will also be allowed if strict distancing rules are followed.

Baker said the rules for levels 3 and 4 were much easier to follow - in level 2 "it needs to be pretty clear to everyone what's involved".

However, he said it was "critical" that everyone gets back to work.

"It's good for health, it's good for the economy".

Alcohol was one concern - a lot of people were gathering and socialising, and the new habits many people had learned in lockdown had gone out the window, Baker said.

Earlier, Baker said Cabinet has a "tough balancing act" to consider when making its decision today.

It needed to weigh up public health against the potential economic impact of extending level 3, he added.

"In many ways [from a health perspective] levels 3 and 4 were easy – people had to stay home unless they had a good reason."

But going to level 2 would be a big jump, given social restrictions would be loosened considerably, compared to the other alert levels, he said.

Levels 3 and 4 were more tightly policed, with specific requirements and restrictions; "level 2 relies on people's individual judgment".

Ardern has previously hinted level 2 could be brought in in phases.

That's something Baker has previously supported.

"Thinking logically, you might begin with the most controlled environments, like workplaces and schools, where risk can be minimised."

Then, once officials are sure level 2 was showing signs of success, the Government could loosen restrictions on places like bars and nightclubs, he said.

Baker has been vocal in pushing the Government to close the borders early in the outbreak and ramp up containment of the virus.

Most recently he's advocated for compulsory masks on public transport and planes. While masks are not thought to protect wearers from getting infected, there's evidence they can stop those wearing them from spreading the virus, through coughing or sneezing, to other people.