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University of Auckland professor Shaun Hendy said an extension could result in New Zealand eliminating the virus completely.
Cabinet was reviewing information collated by Hendy and his team who tracked how Covid-19 spread and how different actions could change the timeline.
On average, the reproductive number of the virus was at 0.5 in New Zealand, meaning on average on half of those with the virus were passing it on to others and the other half were not.
It was "almost certain" to increase if alert level 3 was introduced.
However, the evidence was clear to Hendy – the lockdown was working to eliminate the virus in New Zealand and it should be extended.
"If we stay at this strong level of lockdown we can actually eliminate the virus," he told Newstalk ZB this morning.
"Going to level 3 will be less sure about what that reproductive number will change to, it's almost certain to go up. That's going to prolong the time that we'll have to stay at level 3.
"I think we're close enough to being able to eliminate the virus at level 4 that it [will] be worth staying at level 4 for a little bit longer."
A public announcement would be made at 4pm as to whether the nation would enter level 3.
Cabinet will meet today at 10.30am to deliberate on the move.
The data was only part of the evidence ministers would review today, with opinions from health professionals with infectious disease experiences also included.
Hendy was of the opinion once the nation started recording zero new Covid-19 cases then it would be a good time to drop to level 3.
However, it would be vital for Kiwis not to "let our hair down" and break social distancing recommendations.
If the virus started spreading quickly in alert level 3, then the likelihood of heading into another lockdown would be high, Hendy said.
"We're on track to contain or eliminate the virus here," he told RNZ's Morning Report programme.
"The disease is still spreading, even though the number is below one the disease is still spreading.
"You have to wait sufficiently long for the virus to actually disappear and that's the difficult thing, making a decision on how long you're prepared to wait."
Those who had the virus needed to stay at home and distance themselves from others to ensure they were keeping those around them safe.
Equally, people who had symptoms of the virus should get tested as soon as possible, Hendy said.
A top business leader concedes New Zealand's level-4 lockdown might be extended another five days until after the Anzac Day long weekend,
Failing to exit level 4 would be a "real blow" for business, said Employers and Manufacturers Association chief executive Brett O'Riley, and many firms would need direct financial assistance.
"Possibly they might extend the period of level 4 through to early next week, until after Anzac Day, just to give people more time to get up and going,' he told Newstalk ZB's Mike Hosking.
Although Anzac Day falls on Saturday this year, it is recognised as a public holiday on Monday - and the Government will undoubtedly be thinking about how people will react to an easing of restrictions before a long weekend.
Business was seeking certainty and consistency, said O'Riley.
"We are concerned for areas like retail and hospitality. I think we have been a little bit over the top with some of the requirements in those areas. Either those sectors need to get a little bit more flexibility about being able to open or they will need some direct compensation.
"Those businesses are not in a position to last a few more weeks without being able to operate in some form."
He said manufacturers that probably should have been able to operate at level 4 had exports and supply chains waiting. Australian competitors had been able to continue working and "that's not good".