(Adds detail on offer, background) Sept 20 (Reuters) -...

(Adds detail on offer, background)

Sept 20 (Reuters) - Australia's AusNet Services Ltd (AST) said on Monday it had opened its books to a Brookfield Asset Management affiliate after the energy infrastructure firm received a higher A$9.57 billion ($6.95 billion) indicative, non-binding buyout proposal.

AusNet revealed that the revised bid came after it had rejected two unannounced previous bids from the Brookfield affiliate last month which valued it at up to A$9.38 billion.

The revised A$2.50 per share offer - a 26.3% premium to AusNet's last close - was up from proposals of A$2.35 and A$2.45 tabled earlier.

AusNet said it had agreed to grant Brookfield access to its books and to conduct due diligence on an exclusive basis.

"Should Brookfield make a binding offer at A$2.50 per share then ... it is AusNet board's current intention to unanimously recommend that shareholders vote in favour of the proposal in the absence of a superior proposal," it said in a statement.

($1 = 1.3765 Australian dollars)