The Securities and Exchange Commission has given Foundation notice the pending transaction will not be reviewed.
The deal now requires approval from both companies’ shareholders, who will vote on the merger on July 31.
If approved, the combined company will be the third-largest US coal producer behind Arch Coal and Peabody Energy.
The all-stock transaction, valued at $US2 billion, will give the combined entity a total of 59 coal mines, 14 preparation plants and 2008 pro forma revenues of $4.2 billion.
It will have a very large foothold in the US coal fields, including Foundation’s expansive holdings in the Powder River Basin region, and have total coal reserve holdings of 2.3 billion tons.
The merged company will retain the Alpha name and be headquartered in Abingdon, Virginia.
"We're creating a true US leader in the energy sector with balance, size and scale," Alpha chairman Michael Quillen said.
"Combining our resources and experience puts us in an excellent position to compete in both domestic and international coal markets, using a diverse array of production sources and marketing channels.”
Quillen will become chairman of the combined company and Alpha president Kevin Crutchfield will take up the seat of chief executive officer.
Foundation president and chief operating officer Kurt Kost will become president of the combined company, while James Roberts, Foundation chairman and CEO, will become a member of the board of directors, consisting of six Alpha directors and four Foundation directors.
Alpha and Cliffs terminated their $10 billion merger agreement in November last year, citing the volatile market as well as other issues.