Costco is "working on" a potential expansion beyond Auckland

The US big box retail chain has told Newstalk ZB it's seeing what it can do to extend its offering to other parts of the country.

The company has previously signalled it might open stores in Christchurch and Wellington -- if its first store in Auckland's Westgate was successful.

A Christchurch firm has previously been granted a fixed-term resource consent to open a warehouse in Rolleston, south-west of the city.

Costco says it has nothing to announce right now, but it's "definitely" working on its options.