CHONGQING, China, Sept 24 - The investor relations manager of Chinese aluminium firm Chalco <2600.HK> said on Wednesday she was unaware of any plan for its parent Chinalco to lift its stake in Rio Tinto to 49.99 percent, following a Chinese newspaper report.

China's 21st Century Business Herald quoted Chalco President Luo Jianchuan as saying Chinalco and Alcoa Inc , which jointly bought about 9 percent of the Anglo-Australian miner earlier this year, may consider increasing their stake.

State-owned Chinalco already has approval from Australian authorities to lift the holding to 14.99 percent, a figure which sounds similar in Chinese to 49.99 percent.

Chalco's investor relations manager Zhang Qing said she was unaware of any such plan.

"Chinalco just got approval to raise it to 14.99 percent," she said. "It's unlikely that it would be possible to raise it to 49.99 percent any time soon." Chinalco and Alcoa's acquisition of a $14 billion stake in Rio Tinto threw an obstacle in the path of a takeover bid from rival miner BHP Billiton which could be one of the biggest M&A deals ever if it succeeds.

BHP's bid is under review by several antitrust authorities, since it would further concentrate pricing power in the iron ore trade, something that could trouble Chinese steel makers.

No one at Chinalco was available to comment.