Electric Power Development subsidiary J-Power Australia will also gain a 10-year thermal coal sales contract with Aston starting from first Maules Creek exports in 2014 if the transaction proceeds.

This agreement needs approval from Japanese trading house Itochu, which acquired a 15% stake of Maules Creek for $345 million in December.

Itochu also won pre-emptive rights in its joint venture agreement with Aston last year and could decide to match J-Power’s $370m offer to lift its share of Maules Creek to 25%.

Aston Resources CEO Todd Hannigan was pleased with the agreed terms to sell 10% of Maules Creek to J-Power.

“These commercial terms recognise the development progress made by Aston over the last two years and the underlying value of the world-class Maules Creek Project,” he said.

“Aston is already in a strong net cash position and, following a successful completion of the transaction, would have the majority of the funds required to develop the project.”

J-Power will pay the full $370 million in a single payment once the deal closes and the coal supply contract is expected to start at 150,000 tonnes per annum then gradually ramp up to 900,000tpa.

The deal is also conditional on regulatory approvals, including NSW government consent.

Should it go ahead, Aston would have sold 25% of its Maules Creek to Japanese interests for a total of $715 million. It acquired the whole project off Rio Tinto subsidiary Coal & Allied for $480 million in credit-crunched 2009.

The Maules Creek thermal and semi-soft coking coal project in the Gunnedah Basin is targeting first coal by mid-2013 and aims to ramp up to 10.5 million tonnes per annum of product coal by 2015.

Aston hopes to receive state environmental approval for the project by December.

Shares in Aston were down 3c to $10.03 this morning.