JAKARTA, March 18 (Reuters) - Newmont Mining Corp's Indonesian copper export permit will be extended for six months on Wednesday, a mines ministry official said, after the company gave assurances over its commitment to build a smelter with Freeport-McMoRan Inc.

Earlier this month, the Indonesian government indicated that Newmont's copper export permit would not be renewed beyond March 19 unless it struck a deal with Freeport to invest in the latter's planned smelter.

"We will give an extension of export permit to Newmont," Coal and Minerals Director General Sukhyar told reporters on Wednesday. "I will sign it today. Newmont gave us (a) proposal of their commitment to build a joint smelter with Freeport." (Reporting by Wilda Asmarini; Writing by Michael Taylor; Editing by Prateek Chatterjee)