Arch Coal Inc. says it's started $14.60 a share tender offer for rival International Coal Group.
Arch says the offer that started Monday expires June 14.
The St. Louis-based coal industry giant agreed to buy ICG for $3.4 billion May 2.
The deal is designed to exploit growing demand for high-priced coal used to manufacture steel. Arch says the combined companies would be the nation's second largest supplier of metallurgical coal.