New Zealand and Australia are to step up their assistance for the tiny drought-stricken Pacific island nation of Tuvalu with a joint airlift operation to deploy desalination equipment.

New Zealand Foreign Affairs Minister Murray McCully said Friday that a series of Royal New Zealand Air Force (RNZAF) C130 flights and a Royal Australian Air Force (RAAF) C17 flight would be made in coming days to deploy a large New Zealand Army desalination unit to Funafuti, Tuvalu.

"The RNZAF C130 flight to Tuvalu earlier this week provided smaller desalination units along with Ministry of Foreign Affairs and Red Cross staff. The advice is that more capacity is needed to relieve the acute water shortage and replenish stocks," said McCully.

The first flight in the airlift was a C130 leaving New Zealand Friday afternoon to deliver an advance party of personnel and a forklift.

An RAAF C17 was expected to transport a large desalination plant to Samoa Monday, from where an RNZAF C130 would shuttle the unit to Funafuti over several flights.

"At present the two operating desalination plants at Funafuti are producing a combined volume of 43,000 liters a day. The minimum requirement for the 5,300 residents is 79,500 litres a day, " said McCully.

The new equipment would help ease the critical shortage and provide a sufficient buffer if the dry period continued as expected, he said.

"I would like to thank the Australian government for its assistance in the airlift, allowing a prompt deployment of a large piece of equipment," said McCully.

On Thursday the New Zealand government sent a C130 flight to American Samoa with water containers. It met with US Coastguard vessel Walnut, which has departed Pago Pago for the Tokelau group, which is also experiencing severe water shortages.

The New Zealand Red Cross Tuesday described the severe drought in Tuvalu and Tokelau as "grim" and likely to get worse.

Neither country has seen any significant rainfall for the last six months and none is expected for another two months.

Both countries have declared states of emergency and water rationing has reached critical levels.

Tuvalu has a population of about 12,000 people, who live across nine atolls with a total land area of about 27 square kilometers.

Tokelau comprises three atolls located about 483 km north of Samoa. The atolls are 3 to 5 meters above sea level.