In the aftermath of the federal government's proposal for a mining tax on super profits released on Sunday, US miner Peabody Energy will review the impact of the new tax as it costs up to $US 3.8 billion or $A4.1 billion offer for Macarthur Coal

In a statement released today by Macarthur, the new mining tax will certainly create an uncertainty, especially since Peabody already finished its due diligence on the company and it already clarified and disclosed some information.

Both companies agreed to five-working days of due diligence last month.

Peabody lifted its bid to $16 a share from the original $13 a share, causing Macarthur to halt its planned $1 billion takeover bid with Noble Group's Gloucester Coal.

Macarthur also confirmed last April it will invite other bidders who are interested for bidding negotiations now that Gloucester deal will not push through.

Under the Gloucester deal, Macarthur was not permitted to solicit other bids.

Last Monday, Hong Kong-based Noble Group pulled the plug on its fight for Macarthur Coal.

Macarthur's shares went lower to 10 per cent to $13.86 billion yesterday. It was reported as the lowest since Peabody revealed its bid on March 31, including Peabody's revised offer of $16 a share.

Macarthur is anxious that Peabody might pull the plug after the federal government announced its super-profit tax on Sunday.