U.S. miner Peabody Energy faces an uphill battle to win support for its $3.8 billion bid for Macarthur Coal from the Australian miner's board and biggest shareholder.

Top shareholder CITIC Resources <1205.HK> said it has not yet decided whether to support the A$16 a share offer from Peabody, which trumped a rival bid and led Macarthur to put on hold its own plan to take over Gloucester Coal , a smaller Australian rival.

CITIC Resources, a founding shareholder of Macarthur with 22.4 percent, said it continues to support the rationale for Macarthur's takeover of Gloucester and needed more information to evaluate Peabody's offer.

Macarthur shares were steady at A$16.56 on Monday, 3 percent above the offer price in a weaker broader market, indicating shareholders are not expecting a much higher offer to emerge.

Macarthur is being stalked by other coal producers as it is the world's biggest exporter of pulverized coal, a cheaper, cleaner coal coveted by steel makers at a time when coal prices have nearly doubled on hot demand from China and India.

Under Peabody's offer, Macarthur's top three shareholders -- CITIC Resources and steel giants ArcelorMittal and POSCO <005490.KS> -- would be allowed to retain their stakes.

POSCO, which owns 8.3 percent, has backed the deal in principle and said it plans to keep its stake for now, while ArcelorMittal, with a 16.6 percent stake, said the offer merited consideration.

The two steel producers bought into Macarthur two years ago at A$20 a share, when it was being chased by Swiss-based Xstrata , as they sought to ensure that the company did not fall into the hands of a major coal producer.

Macarthur last Friday said it would enter into talks with Peabody and postponed a vote on the Gloucester deal, which would give Gloucester's main shareholder, Hong Kong-based Noble Group , a near one-quarter stake in Macarthur.

In the meantime it has told shareholders to take no action on any offers.

Peabody's bid last week topped an offer from Macarthur's local rival New Hope Corp .

(Reporting by Sonali Paul; Editing by Balazs Koranyi)