Singtel Optus is close to securing a multimillion-dollar deal with Coles to supply the national broadband network to the supermarket's outlets in a boost to revenue for the government's controversial NBN Co.

Sources close to the negotiations said the agreement is expected to be finalised within the next fortnight and would make Coles a connectivity and internet customer of Optus. The multi-year deal would likely bolster the NBN Co's hopes of securing lengthy contracts with large businesses that can provide a lift in revenue.

Optus is expected to soon become the provider of Coles' internet services over the NBN.

The NBN Co is hoping to make $1 billion a year by 2022 in enterprise revenue and has been looking to do deals with larger companies through telco partners acting as a wholesaler.

A deal with $16.8 billion supermarket giant Coles - Australia's second largest behind Woolworths Group - is considered to be a substantial "vote of confidence" in the NBN, said a source with knowledge of the deal.