(Adds quotes, break-up details) SYDNEY, Feb 23 (Reuters) -...

(Adds quotes, break-up details)

SYDNEY, Feb 23 (Reuters) - Consortiums led by Canada's Brookfield Asset Management Inc and Australia's Qube Holdings (QUB) are considering joining forces to make a A$9 billion ($6.5 billion) bid for Asciano Ltd (AIO), the Australian port and rail giant said.

A new deal would deliver a higher value to Asciano shareholders and speed up approval from the competition watchdog, the two bidding parties said in separate letters to the Asciano board.

The discussions remained preliminary, non-binding and there was no formal agreement yet, leading Asciano to continue to recommend Qube's A$9.01 billion ($6.51 billion) offer.

The joint proposal, which would involve splitting Asciano between the various prospective buyers, marks yet another twist in what would be Australia's biggest buyout from an overseas entity in half a decade. Earlier this month, Asciano dumped an A$8.9 billion bid from Brookfield after Qube upped its offer.

In a letter to Asciano Chairman Malcolm Broomhead, Brookfield Chief Executive Officer Sam Pollock said the revised buyout would improve the chances of approval from the Australian Competition and Consumer Commission, which has said it is concerned by elements of Brookfield's and Qube's bids.

Under the new proposal, several of Brookfield's and Qube's bid partners, including China Investment Corp, would take Asciano's national rail freight business, while Qube and Brookfield would join to buy its ports business.

"The basis for the discussions is to seek to develop a proposal that ... is capable of achieving expeditious ACCC review and provides greater certainty as to timing of completion," Pollock wrote in his letter, published by Asciano.

Asciano said it remained committed to Qube's proposal "in the absence of a superior proposal capable of acceptance". ($1 = 1.3826 Australian dollars)