Work on a new coal face in Warwickshire has been delayed.
UK Coal said it would start work on the face at Daw Mill colliery at the end of March, a month later than planned, due to difficult geological conditions.
The firm, the largest coal mining company in the UK, has said there may be further production delays after a "difficult" final quarter in 2009.
The company also has deep mines at Thoresby and Welbeck in Nottinghamshire.
A spokesman said the company remained focused on getting the new Daw Mill face into production.