There are 140 people on a priority list for evacuation from Kaikoura, Prime Minister John Key says.

The first US warship to visit New Zealand in decades has been drafted in to help humanitarian efforts as the Government continues to help stranded tourists in Kaikoura out of the area.

And now Australia has announced frigate HMAS Darwin is steaming south diverted along with American destroyer USS Samson from Auckland's 75th New Zealand Navy celebrations.

The North Canterbury region was worst-hit by the 7.5 magnitude earthquake, with landslides and slips blocking all road access in and out of the tourist town.

SUPPLIED Prime Minister John Key confirmed the USS Sampson's two on-board helicopters could join the disaster relief effort and the Malaysian Government has also offered a helicopter.

Meanwhile, a United States Marine Corps P-3 Orion maritime patrol aircraft currently participating in New Zealand exercises will also join relief efforts.

READ MORE:

* Largest navy ship in NZ to help stranded tourists

* Flights out of Kaikoura ramp up

* PM John Key: Utter devastation

* Photos: Large earthquake hits

The Orion from Hawaii based Patrol Squadron (VP) 47 will conduct aerial assessments of earthquake affected areas around Kaikoura.

SUPPLIED Australian navy guided missile frigate HMAS Darwin is joining Kaikoura earthquake relief efforts

Squadron commanding officer Commander Ryan C. Cech said he's "proud we can assist our New Zealand partners in their time of need."

Defence Minister Gerry Brownlee said NZDF has now accepted offers of help from the US, Australia, Canada, Japan and Singapore.

"The USS Sampson, an Arleigh Burke-class destroyer, has departed from the Hauraki Gulf and is now on its way to Kaikoura, where it will deploy two MH60 helicopters to help as require.

HANDOUT A United States Marine Corps Orion will conduct aerial assessments of quake torn Kaikoura.

"The Australian Defence Force has diverted the HMAS Darwin from her planned participation in the International Naval Review.

"The Darwin is expected to arrive off the Kaikoura coast on Wednesday evening and will deploy its Seahawk helicopter from offshore. Canada is sending its frigate the HMCS Vancouver.

"The New Zealand Navy has already sent HMNZS Canterbury and HMNZS Wellington to Kaikoura and it will also send frigate HMNZS Te Kaha and tanker ship, HMNZS Endeavour.

Martin Hunter Tourists trapped by the Kaikoura earthquake arrive by military helicopters at Woodend School grounds in Christchurch.

"It's heartening to see overseas partners so willing to alter their plans and offer their assistance.

Combined, the Samson, Darwin and Vancouver carry four helicopters capable of carrying several passengers each while lifting tons of relief supplies.

A New Zealand Defence Force spokesman said it was unclear when the USS Samson would reach Kaikoura.

IAIN MCGREGOR/FAIRFAX NZ Aerial surveys offer a snapshot of some of the earthquake devastation relief personnel face.

NZDF could not confirm its exact role in how it will help with humanitarian relief, but it was expected to become more clear on Wednesday.

The HMNZS Canterbury is also en route from Auckland and was expected to dock on Wednesday.

About 200 tourists have already been airlifted out of Kaikoura by NZDF.

Sam Sherwood Stranded tourists put their names down a helicopter flight out of Kaikoura.

Earlier on Tuesday, Prime Minister John Key confirmed the USS Sampson's two on-board helicopters could join the disaster relief effort and the Malaysian Government has also offered a helicopter.

Key, Finance Minister Bill English and Brownlee fronted yesterday morning to provide an update on latest developments.

Things weren't going to revert to normal quickly. "It's going to take quite some time to get back to the way [things] used to be," English said.

There was significant infrastructure damage in Wellington, obvious damage in Kaikoura, disruption to transport links would be major, with both the Picton and Wellington ports sustaining damage, and the main arterial route from the North to the South Island would be disrupted for "quite some time".

"This is going to add up to something fairly significant," English said.

Damage to State Highway 1 and other infrastructure was so severe transport authorities may look at realigning parts of the network.

"The slips are of a scale that are very meaningful . . . so one of the questions will become, in rebuilding the road, is it absolutely in the right place? Is rail in the right place? And how susceptible is it to a future earthquake or slip?" Key said.

The cost remained in "the billions" and damage to Wellington could be significant.

Key said the lesson from Christchurch was that damage which initially appeared innocuous could end up being quite serious.

"Wellington damage could [potentially] be not insignificant."

The Government was relying on people having their own insurance but in circumstances where that was not the case it would "potentially look to give them some support".

Meanwhile, Economic Development Minister Steven Joyce would look at a business continuity and support package.