Optus has launched a $1 billion effort to improve regional coverage.

Optus says the money will be spent over the year to June 2018 on 500 new mobile sites across regional and remote locations, 114 of which are inside the government's mobile blackspots program boundaries.

The telco also intends to upgrade over 1800 sites from 3G to 4G, and add 4G capacity to around 200 sites to better handle peak usage periods.

A majority of the money will be spent in NSW, Queensland, and Victoria.

“This represents one of the single largest investments in regional mobile infrastructure in Australia’s history,” Optus CEO Allen Lew said in a statement.

“I challenge regional Australians to put Optus’ network to the test for themselves. Try our network and if you’re not satisfied, simply contact us within 30 days to cancel the service, return the handset in good working order, and there won’t be any plan cancellation fees.”

The spending spree matches a pledge by Optus’ major rival Telstra last year, which also involved about $1 billion in funding for improved mobile coverage in remote and rural areas over five years.

The investments come amid a battle over the ACCC’s decision not to force mobile providers to let other roam on their networks.

Vodaphone had argued that being kept off regional roaming harmed competition, but Optus and Telstra say giving other companies access would make investments like theirs less likely.