* Elliott calls for BHP board "upgrade"
* Lists outside investors seeking change
* Latest Elliott missive comes as new BHP chairman looms (Adds comment from AMP, details of BHP board meeting)
SYDNEY, June 14 (Reuters) - Activist shareholder Elliott Management called on BHP BHP.AX BLT.L on Wednesday to "upgrade" its board of directors as the mining giant prepares to select a new chairman this week.
"BHP has an entrenched board, with long-tenured directors having approved the disastrous acquisitions and poorly timed share buybacks that are at the root of much of today's underperformance," Elliott said in a statement.
"A significant upgrade in directors is needed."
Elliott, a New York-based fund that has built up a 4.1 percent stake in BHP, has maintained a barrage of criticism of the global miner since releasing a list of changes it wants at the company, including an exit from its U.S. oil shale business.
BHP's board of directors is currently meeting in Chile, home to the company's vast copper mining business, where it is expected to select a new chairman. wealth management group Escala and fund Tribeca Investment Partners have also campaigned for a revamp at the company, with calls for board changes and reviews of the energy divisions.
In a note last week, AMP Capital, one of BHP's largest shareholders, called on the miner to conduct an "independent assessment" of Elliott's proposal to unify BHP's dual-listed company structure and to "prove the worth of its U.S. onshore business and why it is compatible in the BHP portfolio."
BHP was not immediately available to comment.