A group of investors including buyout firm Apollo and pension...

A group of investors including buyout firm Apollo and pension fund Canada Pension Plan (CPP) is bidding for coal assets put up for sale by mining giant Rio Tinto , which could fetch $2 billion, sources familiar with the matter told Reuters.

The sale, run by Credit Suisse, of the Kestrel and Hail Creek coking coal mines is part of Rio's (RIO) planned exit from Australian coal to focus on iron ore, copper and aluminum.

Interested parties have been invited to submit tentative offers by a Dec. 8 deadline.

Apollo Global Management and the CPP have joined forces with U.S. coal company Xcoal Energy & Resources and a former Glencore executive to bid for the assets, two sources said.

They added that Anglo American had expressed an interest but the deteriorating outlook for met coal, whose third-quarter contract price fell by five percent, might deter it from making a formal bid in December.

Australia's Whitehaven Coal was also likely to put in an offer, one of the sources said.

Rio Tinto has just completed the sale of its Australian Coal & Allied thermal coal unit to China-backed Yancoal Australia (YAL) for $2.69 billion.

Rio is viewed as having the strongest balance sheet in the sector, with little debt and a mounting cash pile from its low-cost iron ore operations and possibly more asset sales.

Rio, Anglo American and Whitehaven Coal declined to comment. Apollo, XCoal Resources, and the CPP were not immediately available to comment.