June 17 (Reuters) - U.S. coal producer Peabody Energy BTU.N has locked out workers at its United Wambo Washery in New South Wales for two weeks, Australia's Mining and Energy Union (MEU) said on Wednesday, escalating a pay dispute.

Workers have been taking protected industrial action since early May after rejecting an offer that included annual wage increases of 2.5% and changes to bonus arrangements, the union said.