Macarthur, the world's largest miner of pulverised coking coal used as a low-cost input in steel making, said it had received a formal statement from the joint US-European "bidding vehicle" and advised shareholders not to act.

"While a superior offer from an alternative interested party cannot be assured, Macarthur is in continuing discussions with other interested parties," the Queensland-based miner said in a statement to the Australian bourse (ASX).

"Macarthur also notes that the Marcarthur share price has remained consistently above (the) offer price of Aus$15.50 (US$16.50) per share since the offer was announced on 1 August," it added.

Macarthur said the offer, open for acceptance until at least mid-September, was "conditional, requires various regulatory approvals and is not stated to be final in any respect -- i.e. it is capable of being improved."

"The Board of Macarthur will review the offer and provide advice to shareholders... in sufficient time for shareholders to make an informed decision regarding the offer," the miner said.

"In the meantime shareholders are advised to take no action in relation to the offer... until they receive further communications from the board," it added.

Jointly vying for Macarthur under the banner PEAMCoal, Peabody and ArcelorMittal launched a hostile bid earlier this week after the Australian miner refused to back their initial friendly offer.

The consortium -- 60 percent Peabody and 40 percent ArcelorMittal -- urged Macarthur shareholders to accept the offer as "compelling and representing outstanding value for your shares" in a letter lodged Thursday with the ASX.

"Macarthur shares have substantially underperformed other Australian resource stocks despite rising coal prices and record demand," PEAMCoal said, estimating a lag of 30 percent behind other miners in the past year.

"Our offer provides you with a substantial premium over Macarthur's relevant trading ranges, not only in its recent history but over and extended time frame," it added.

PEAMCoal said its offer was a 41 percent premium to Macarthur's value prior to the original bid and it only needed another 34 percent of the company's shares to meet the minimum acceptance threshold.

Anyone who held out beyond PEAMCoal gaining a majority stake put the value of their shares at risk, the letter added, urging Macarthur holders to "accept the offer as soon as possible".

Macarthur shares closed 0.19 percent higher at Aus$15.78 in a broadly lower market.

Copyright AFP (Agence France-Presse), 2011