UPDATE 1-SAfrica union in standoff with Implats over wages

* Union wants 20 pct wage rise, Implats offers 6.5 pct

* Company says to take next step if union decalres dispute

(Adds Implats spokesman)

JOHANNESBURG, June 25 (Reuters) - South Africa's National Union of Mineworkers said on Thursday it had rejected a 6.5 percent wage offer by Impala Platinum (IMPJ.J), the world's second largest producer of the precious metal.

The union, which has demanded a wage increase of 20 percent, more than twice the consumer inflation at 8 percent, declared a dispute over the pay issue and said it would refer the matter to a mediator to resolve. Failure to reach a resolution could result in a strike.

The appointed mediator is the Commission for Conciliation, Mediation and Arbitration (CCMA), the union said.

"We totally reject this kind of harassment and are referring the matter to CCMA today, failure to find common ground will result in the CCMA issuing a certificate of non-resolution," said Eddie Majadibodu, the NUM 's negotiator at Impala.

Bob Gilmour, a spokesman for Implats, said the company was yet to receive a letter confirming that the union had declared a dispute, but would take the matter to the next step once it received the communication.

(Reporting by James Macharia; Editing by Keiron Henderson)