The Secretary shall establish a process for the voluntary mediation of disputes pending before the Office. The mediator shall be agreed to by all parties involved in mediation and shall be independent of the parties to the dispute. In the mediation of disputes the Secretary shall consider mitigating circumstances and proportion of harm pursuant to section
1234b of this title. In accordance with rule 408 of the Federal Rules of Evidence, evidence of conduct or statements made in compromise negotiations shall not be admissible in proceedings before the Office. Mediation shall be limited to 120 days, except that the mediator may grant extensions of such period.