Activist investor Elliott Management renewed calls a shake up at BHP (BHP)  Tuesday, claiming broad investor support for its plan to sell some or all of the mining giant's US oil assets.

Elliott has been lobbying for a change in BHP strategy since April 10, and this weeks sharpened its, claiming the oil business held the key to boosting shareholder returns while abandoning earlier demands that the company consider dropping its Australian listing.

The Melbourne, Australia-headquartered mining company has already rejected calls from Elliott to spin off and list its US oil business, claiming that it has conducted reviews of the unit on two occasions and found that a sale would undermine BHP's diversification and that the oil operations were fairly valued within the group.

BHP shares were marked 0.15% lower in the opening hour of trading in London and changing hands at 1,188 pence each, extending their year-to-date decline to just over 9%.

Elliott, which owns 4.1% of BHP's UK-listed business, remains unconvinced and called on BHP's CEO Andrew Mackenzie to launch an independent review of the business. Elliott's push appears timed to coincide with a presentation by Mackenzie at a Bank of America Merrill Lynch mining conference that begins Wednesday.   

"There is extremely broad and deep-rooted support for proactive steps to be taken by management to achieve an optimal value outcome for BHP's petroleum business following a formal open review," Elliott wrote in a letter to BHP's management.

Elliott, led by Paul Singer, claimed that carving out and listing BHP's shale and deepwater oil operations, would create a business worth as much $22 billion, or about $15 billion more than Elliott believes it is worth within BHP. Those demands won qualified support from Australian boutique investment fund Tribeca Investment Partners, which said earlier this month that BHP should abandon its US shale assets, but retain its US deepwater operations located in the Gulf of Mexico.

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