In their submissions to the Australian Securities Exchange, the two companies said they would announce a proposed transaction between each other.

AWE had confirmed on April 14 that it was holding talks with Arc following reports that it was planning to make a friendly $500 million bid for the smaller company.

The acquisition of Arc will give AWE bigger stakes in its existing projects in the Bass Strait and Perth Basin, and open up new opportunities in onshore Western Australia.

AWE's stake in the Origin Energy-operated BassGas development will increase by 12.5% to 42.5%, while its stake in the Roc Oil-operated Cliff Head field in Western Australia will more than double to 57.5%.

Both companies said the trading halt would end when the announcement is released on April 28.