An air drop of vital supplies will be made to a trans-Tasman kayaker first thing tomorrow morning.

Scott Donaldson, 34, is attempting to cross the Tasman Sea by kayak.

The Rotorua man left Coffs Harbour on the NSW coast on April 19, and is hoping to land in New Plymouth.

Although an air drop was scheduled for Saturday, due to a broken rudder, Donaldson is running low on water and the drop was pushed forward.

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Rescue pilot John Funnell, who is based in Rotorua, said a drop was planned for first light on Thursday.

He said a broken rudder had slowed Mr Donaldson's progress, and he planned to drop some much needed water and a repair kit.

Mr Funnell confirmed Donaldson is 265 nautical miles from the New Zealand coast, and is paddling through winds of up to 30 knots.

He said fortunately these winds are blowing Mr Donaldson towards New Zealand.

Storms on both sides of the Tasman have meant rough conditions for Mr Donaldson, who has also had to contend with heavy rain.

Mr Funnell said he was in contact with Mr Donaldson once a day, and is updated on his position twice a day.

Mr Donaldson has stated he is kayaking to raise awareness of the importance of increasing aerobic activity levels in our day to day lives.

This is his second attempt to cross the Tasman, after his kayak filled with water two days into his his first attempt in May last year.