Coles is reportedly close to securing one of the biggest retail acquisitions in Australian corporate history, with the supermarket giant understood to be finalising a deal worth more than $4 billion for Petbarn owner Greencross.

According to reports, negotiations between Coles and private equity owner TPG are now largely complete, with an announcement expected as early as this week.

The acquisition would dramatically expand Coles beyond its traditional supermarket business, giving the retailer an Australia-wide footprint in pet retailing, veterinary clinics and specialist animal healthcare.

Greencross operates 247 Petbarn stores across Australia, along with 143 veterinary clinics, 28 specialist and emergency animal hospitals, and a 50% stake in New Zealand pet retailer Animates.

The move also positions Coles more directly against Woolworths, which acquired a controlling 55% stake in rival pet retailer Petstock four years ago.

Greencross combines retail operations with veterinary services, not only creating recurring customers but also multiple revenue streams that are less dependent on supermarket margins. For Coles, the attraction of this deal goes beyond selling pet food.

Coles exited its own online pet marketplace, Swaggle, earlier this year following weaker-than-expected performance. Rather than building its own pet business, the retailer appears to be opting to acquire the country’s largest established operator.

While the transaction strengthens Coles’ long-term diversification, investors remain cautious about the price.

Shares in Coles fell more than 4% after the company confirmed earlier this month that it was undertaking due diligence on Greencross.

If completed, the acquisition would cement pet care as one of Australia’s fastest-growing retail categories.