Mumbai: Australian coal mining company Resource Pacific Holdings has rejected a sweetened cash offer by Xstrata, the world's largest exporter of thermal coal, saying it was "unimpressed" by the offer which valued it a little over $1 billion.

The Swiss-based Xstrata increased its unconditional cash offer from A$2.85 ($2.55) per share to A$3.20 ($2.86), valuing Resource Pacific at A$1.08 billion (US$964.8 million).

Xstrata said the new offer price of $3.20 a share, which was 12 per cent higher than the $2.85 previous offer, was final.

Resource Pacific is currently mining one of the largest identified semisoft coking coal seams in the Hunter Valley of New South Wales state, with more than 252 million tonnes in reserve.

The miner had rejected an all-share approach by New Hope, five days after Xstrata launched its first offer in last December.

Xstrata's revised offer came just hours before the original offer was to expire.

Resource Pacific managing director Paul Jury said the bid was "unimpressive". But, he said the company's board would meet soon to discuss the improved offer and would then advise shareholders accordingly.

The revised offer is scheduled to close on February 22. Xstrata said the revised offer price surpassed Resource Pacific's trading high and that there was currently no competing offer.

"Xstrata's revised cash offer is priced at a 108 per cent premium to the average price of Resource Pacific shares before the commencement of take-over activity," it said in a statement.

Xstrata chief executive Peter Freyberg said the takeover would insulate Resource Pacific shareholders from production issues at Newpac and market volatility.

The Newpac mine in the Hunter Valley of New South Wales is Resource Pacific's sole asset. Resource Pacific plans to double production at its Newpac mine to eight million tonnes a year, which Xstrata says is unrealistic.

"In the absence of Xstrata's offer, shareholders may face an uncertain future, being fully exposed to the business impact of the cumulative production shortfalls from the Newpac mine and future mining risks," Xstrata said.