(Adds Duet response, Ausgrid background) SYDNEY, Dec 5...

(Adds Duet response, Ausgrid background)

SYDNEY, Dec 5 (Reuters) - Hong Kong-listed Cheung Kong Infrastructure Holdings Ltd <1038.HK> has made an A$7.3 billion ($5.44 billion) bid for Australian energy infrastructure owner Duet Group (DUE), Duet said on Monday.

Duet said it had received an "an unsolicited, indicative, incomplete, non-binding and conditional proposal," offering A$3 per share in cash.

The offer represents a 27.7 percent premium to Duet's Friday closing price of A$2.35.

Duet said its board was considering the proposal, and advised shareholders to "take no action as there is currently no certainty the proposal will proceed further".

The offer comes after CKI's bid for Australian electricity grid Ausgrid was rejected in August by the country's Foreign Investment Review Board (FIRB).

FIRB must also approve CKI's takeover of Duet for it to succeed and the deal is subject to the approval of Duet shareholders. ($1 = 1.3428 Australian dollars)