(Recasts, adds Qube quote, shares, deal context) SYDNEY, March...

(Recasts, adds Qube quote, shares, deal context)

SYDNEY, March 15 (Reuters) - Shares of Australian port operator Qube Holdings Ltd (QUB) and Asciano Ltd (AIO) were suspended on Tuesday, after Qube said it would soon make a "significant" announcement about an acquisition following after a months-long bid against Canada's Brookfield Asset Management Inc to buy Asciano.

In a Tuesday letter to the Australian Securities Exchange that Qube released, the company requested a trading halt "as it believes it will shortly have a significant announcement to make in relation to an acquisition and capital raising."

Asciano also said in a statement it had requested a trading halt as the company expected to make an announcement shortly in relation to recent media speculation about a merger.

Qube's letter did not specify the takeover target. But on Feb. 24 Qube said it wanted to end the bidding war with Brookfield, and instead join forces to buy Australia's biggest ports and rail freight company with a joint bid worth A$9.1 billion ($6.8 billion).

A Brookfield spokesman declined to provide immediate comment. Asciano did not return calls for comment.

Qube and Brookfield announced their 50-50 joint venture in February to buy Asciano's ports division, saying their financial backers, which include China Investment Corp [CIC.UL] and Canadian pension funds, would acquire the railways.

Asciano had initially backed Brookfield's stand-alone offer of cash and shares last year but changed its preference earlier this year after Qube raised its offer. It has said that while it would consider a joint Qube-Brookfield offer, it would continue to support the Qube offer until it has a concrete alternative offer.

Asciano shares closed at A$8.87 on Monday, below Qube's A$9.28 per share offer but up 40 percent from a year earlier.

($1 = 1.3321 Australian dollars)