BHP Billiton Ltd. (NYSE: BHP) has hired Barclays to divest its U.S. Fayetteville Shale gas assets as the miner seeks to fend off an attack by activist funds, two sources close to the matter said May 23.

BHP said last month its gas-rich Fayetteville Shale assets in Arkansas was under review and that it was "considering all options, including divestment".

BHP declined to comment and Barclays was not immediately available for a comment.

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The miner had tried to sell the business more than two years ago, but the attempt was shelved in February 2015, when it said it planned to "maximize value" of the assets.

The revived sale comes as activist investor Elliott Advisors, which has built up a 4.1% stake in BHP's London-listed arm, urged for changes to boost shareholder value.

The sale is expected to draw interest from smaller mining companies already operating in the region, the sources said.

The Fayetteville assets, which BHP acquired for $4.75 billion in 2011, had a book value of $919 million at the end of 2016, according to the company's annual accounts.

The miner had to write down the assets by $2.8 billion in 2012 due to lower gas prices.

Earlier this month, Elliott called for BHP to run an independent review of its petroleum division, valued at more than $20 billion, after asking to spin off the U.S. oil and gas assets.

BHP has rejected the call by Elliott, which was later joined by Australian boutique manager Tribeca Partners.

The mining company denied any link between the activists' move and prospects for Fayetteville including divestment and said the move was instead part of an ongoing review.

Within the petroleum business, BHP has long made it clear it intends to focus on liquid products in the U.S., a more lucrative business than dry gas.

In February, it agreed to spend $2.2 billion to fund its share of investment for the second phase of the Mad Dog oil field in the Gulf of Mexico.