SYDNEY (Reuters) - Canada's Brookfield Asset Management Inc (>> Brookfield Asset Management Inc) and its Australian rival are weighing a joint A$9 billion ($6.5 billion) bid for Australia's biggest rail and port operator, an unusual measure aimed at ending the fiercest takeover battle now raging in the Asia Pacific after seven months.

Target firm Asciano Ltd (>> Asciano Ltd) revealed on Tuesday that Brookfield and the company it has been bidding against, Australian cargo handler Qube Holdings Ltd (>> Qube Holdings Ltd), have entered talks about a possible joint offer.

The ceasefire, if it leads to a concrete offer, would deny the rival firms full control of the Australian freight giant but would spare further delays in clinching a deal as they outbid each other.

It could also circumvent a run-in with regulators, particularly the Foreign Investment Review Board, as the proposal under discussion involves giving Brookfield and Qube joint ownership of Asciano's ports - which the government views as strategic assets that should remain in Australian hands - while their foreign bid partners would own the railways.

Reuters previously reported that Brookfield has partnered with the Qatar Investment Authority and the Canadian Pension Plan Investment Board, while Qube has teamed up with government-owned China Investment Corp. [CIC.UL]

"Any proposal for more Chinese interest in ports would be likely to be sensitive," said an M&A lawyer who also asked not to be named because of the sensitivity of the matter.

"Provided this aspect is managed well, I expect that FIRB would be fine with what I understand to be predominantly Canadian and Australian interests taking control of these assets," they added.

Qube shares rose more than 10 percent on hopes that a joint offer might end the stand-off. Asciano shares rose 1.5 percent.

Brookfield declined to comment on the proposal while a Qube spokesman was not immediately available for comment.

A week earlier, Asciano quit its support for the stand-alone bid Brookfield made last July after Qube upped its counter-offer and added CIC to its consortium. Brookfield responded that it would raise its bid and take in outside investors.

On Tuesday, a source familiar with that situation told Reuters that since then, Brookfield and Qube had started talks aimed at a joint proposal that would give Brookfield and Qube joint ownership of the ports and their bid partners the railway.

The proposal would also distance Brookfield from Asciano's railways, as Brookfield already has rail assets in Australia.

"It's just about short circuiting what was going to be a long and involved and potentially costly process between two parties who clearly wanted the asset badly," said the source, who asked not to be named because of the sensitivity of the situation.

Asciano said the discussions remained preliminary and that it would continue to recommend Qube's proposal in the absence of a higher bid.

($1 = 1.3833 Australian dollars)

(Additional reporting by Elzio Barretto in HONG KONG; Editing by Stephen Coates and Miral Fahmy)

By Byron Kaye and Swati Pandey