From midnight tonight, all Melbourne residents will be banned from crossing into NSW.

From midnight tomorrow, all Victorians will be banned from entering NSW, including Wodonga residents.

Police and Defence personnel will be stationed at all border crossings.

Self-isolation measures will be in place.

Residents can cross the border for essential health or work reasons with a travel exemption permit, though should expect delays.

NSW Premier Gladys Berejiklian said following talks with Mr Andrews and Mr Morrison the border would close midnight Tuesday.

"We wouldn't have taken this step unless we absolutely had to," she said.

Ms Berejiklian said community spread is increasing in Melbourne and she is concerned about it spreading to regional Victoria.

How do I apply to cross the border?

Soon, Service NSW will have online applications for travel exemptions.

These exemptions will allow residents to cross the border throughout the closure. It's believed you will not need to apply for a new exemption every time you need to cross the border.

However, the service is not yet accepting applications and it's expected the infrastructure won't be in place for another two to three days.

The NSW Premier has not defined what will be classed as essential travel but indicated people who need to cross the border for work or school will be eligible.

Ms Berejiklian said people in need of critical health care can cross the border.

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"Clearly if your child goes to the school across the border that is fine as well," she said.

"We know the next two to three days will be extremely difficult for border communities, we anticipate there will be long queues, we anticipate police will have their work cut out for them."

She warned that the first two to three days would be very difficult on Border communities while infrastructure was set up to allow for the exemptions.

She said to expect delays and queues as police check cars across the border.

Special conditions will be in place for freight operations and other critical services.

What will happen if I try to cross the border anyway?

Police commissioner Mick Fuller said they would be seeking additional powers for on the spot fines. He said they were especially looking for powers to punish those who mislead police in their exemption applications.

Currently there is a $11,000 fine and up to six months in jail for COVID-19 breaches.

"The NSW Police Force is ready to step up, 400 police officers plus other agencies are preparing to enforce the closure of the NSW and Victorian border," Commissioner Fuller said.

Mr Fuller said about 400 police offices as well as defence personnel would be monitoring crossings including the four mail arterial roads and 55 odd bridges while drones and aerial surveillance would watch the rivers and bushland.

He said for now, it would be a very slow process to cross the border.

"There will be delays as we work through those who are essential workers," he said.

Some plane and train travel between the states will continue to allow residents to return to their stat-of-origin, but permits will be need after midnight Tuesday.

When will the border reopen?

Ms Berejiklian would not say when the border would reopen, or even when the decision would be reassessed.

She hopes the closure is a temporary measure but it comes down to the health advice.

"if you're not in control of the virus you're not in control of the economy," she said.

"I don't want to see this happen for a long time."

Ms Berejiklian said some flights, train services will be available but only for those who have permits or are returning NSW residents.

"They will have to self isolate," she said.

Ms Berejiklian said anyone with even those mildest symptoms need to be tested.