The operator did not indicate when shipping would commence, but said the agreement would extend for eight months.

"The time, expense and effort that have gone into establishing Horizon mine as a valuable source of compliant coal for the world's power producers are yielding us tangible, positive results,” America West chief executive officer Dan Baker said.

“In view of the new domestic and international coal supply contracts we've announced over the past several weeks, the outlook for America West's 2010 financial performance continues to strengthen, helping to fuel a tremendous sense of pride and enthusiasm at our company."

The supply deal is the company’s third to be signed in the past month, though it is the first domestic transaction during that period. In late April, it signed a four-year, $200 million transaction with an undisclosed China-based energy firm.

The master coal purchase and sale agreement is based on predetermined contract pricing and is valued at $47-51 million per year for four years.

Just a week before, the producer inked a large multi-year master coal purchase and sale agreement with a large European electricity trader.

The deal with the undisclosed customer, valued at about $9.4 million, provides for America West to ship compliant coal monthly on a predetermined shipping schedule beginning in April and extending through December 2013.

In total, the Horizon mine has about 19 million tons of coal reserves under lease.