National carrier Air New Zealand said around 30 percent of its international flights are likely to be cancelled starting next week as a result of a series of planned strikes by its union members.

Air New Zealand General Manager International Airline Ed Sims said a total of 14,000 passengers will be affected by the series of 48 hour strikes planned to start on July 18, 21 and 24.

"Whilst we have negotiated with FARSA (the union representing 1,000 long haul crew members) in good faith, we are still some way apart in terms of reaching agreement," Sims said, in a statement issued late on Wednesday.

"We have been left with no options but to implement a contingency plan that will see the travel arrangements of around 14,000 New Zealand and overseas customers affected."

He said that 15 to 20 international flights a day, on average, will be cancelled on the proposed strike days. No domestic flights will be cancelled.

All direct services between New Zealand and Los Angeles, San Francisco, London and Tokyo will operate as scheduled.

Some flights to Australia, Singapore, Hong Kong, Taiwan and Japan's Nagoya and Kansai airports are likely to be affected by the strike.

Air New Zealand said union members have been demanding improvements in pay and annual leave that would cost NZD$14.2 million (USD$9.5 million) over a three year period.