* Top Extract shareholder Kalahari faces Chinese takeover proposal
* Chinese need exemption from rule requiring it to bid for Extract
* If Chinese took over Kalahari, would own 43 pct of Extract
* Extract shares jump 8.6 pct to 18-month high (Changes lead, adds Itochu comment, advisers, updates shares)
By Sonali Paul
MELBOURNE, March 9 (Reuters) - Australia's Extract Resources piled pressure on a Chinese nuclear power producer, which has bid for its main owner, to extend the takeover offer to its other shareholders, a move that may more than double the China firm's acquisition costs to $2.7 billion.
A unit of China Guangdong Nuclear Power Holding Corp (CGNPC) is lining up a $1.23 billion offer for Kalahari Minerals , Extract's top shareholder with a 43 percent stake, in a deal that would help it secure uranium from Africa.
The prospect that the bid for Kalahari may automatically trigger a buyout of Extract under Australian takeover rules helped send its shares to an 18-month high on Wednesday.
Extract said on Wednesday CNGPC is seeking an exemption from the takeover rule that would automatically force it to make an offer for the rest of Extract's shares if it gains control of Kalahari.
Extract said it would ask the Australian Securities and Investments Commission to grant that relief to CGNPC on condition that "all Extract shareholders are not disadvantaged in any way" or not grant the relief.
Extract's shares had already jumped on Tuesday as investors bet that the move on Kalahari would spark a bidding war between the Chinese company and Kalahari's 14 percent shareholder, global miner Rio Tinto .
"Rio could block a bid or turn around and bid themselves. This is going to be interesting," said Ric Ronge, a portfolio manager at Pengana Capital, which does not own shares in Extract.
< A1>
URANIUM THIRST
Uranium is key to China's push to use cleaner energy, with 28 nuclear reactors under construction as the country races to meet soaring energy demand.
The main attraction in Kalahari is its stake in Extract, which is developing the Husab uranium project in Namibia, which it says is the world's fifth-largest uranium-only deposit, close to Rio Tinto's Rossing uranium mine.
Extract shares jumped as much as 8.6 percent on Wednesday and last traded up 8 percent at A$10.73, valuing the company at A$2.7 billion.
Extract's share price rise is in line with the value of CGNPC's bid for Kalahari, reflecting the fact that Kalahari's main asset is its 43 percent stake in Extract.
If CGNPC took over Kalahari, it would own more than 20 percent of Extract, the threshold at which Australian rules would require it to make a takeover offer for Extract.
If the exemption is not granted, the Chinese company would be required to make a matching takeover offer for Extract Resources.
The commission typically aims to respond to submissions within 21 days but can consider applications like this more swiftly.
Whether the Chinese company is forced to bid for Extract or not, it will run into Rio Tinto and Japanese trading firm Itochu Corp , which are major shareholders in both Extract and Kalahari.
Itochu has not made any decisions about its stakes, a spokesman in Tokyo said, declining to comment further.
CGNPC is waiting to see Rio Tinto's response to the proposed bid for Kalahari, a CGNPC official said, declining to comment further. The official declined to be named as he was not authorised to speak to the media.
Extract Resources declined to comment further on its planned submission to the commission. Rio Tinto had no comment.
Rothschild is advising Extract, Deutsche Bank is advising CGNPC, and Azure Capital and Ambrian Partners are advising Kalahari. (Additional reporting by Taiga Uranaka in TOKYO and Xu Wan in BEIJING; Editing by Muralikumar Anantharaman)