Notwithstanding subsection (d) of this section and section
1399
(c) of this title, if an employer contests the plan sponsor’s determination under paragraph (1) through an arbitration proceeding pursuant to subsection (a) of this section, or through a claim brought in a court of competent jurisdiction, the employer shall not be obligated to make any withdrawal liability payments until a final decision in the arbitration proceeding, or in court, upholds the plan sponsor’s determination.