US behemoth, Costco, is ramping up its Australian expansion, with the membership-only retailer likely to add more than five stores by 2015.

The warehouse supermarket is set to expand into Adelaide and Brisbane, and is investigating additional sites in Sydney and Melbourne.

Costco first entered Australia in 2009 and has since expanded to three stores in Melbourne’s Docklands, Auburn in Sydney’s west, and Canberra.

It is now eyeing off another Sydney site in the southern suburb, Caringbah, as well as a plot in Melbourne’s outer city suburb, Epping.

It is locked in to anchor the Sydney Business Park development in Marsden Park, and is building a store at Churchill Centre in Kilburn in Adelaide.

Costco is also said to be looking into various locations in Queensland, such as Logan, Brisbane’s western suburbs, and the Gold Coast.

The US giant is based on membership retail, where customers pay a yearly fee to access the chain’s selection of bulk grocery and household objects.

The warehouse retailer requires footprints between about 13,000sqm and 15,000sqm, with the potential site in Caringbah pushing 16,000sqm.