(a) On request of a party in interest at any time within 180 days after the date of the entry of an order of confirmation under section 1325 of this title, and after notice and a hearing, the court may revoke such order if such order was procured by fraud.

(b) If the court revokes an order of confirmation under subsection (a) of this section, the court shall dispose of the case under section 1307 of this title, unless, within the time fixed by the court, the debtor proposes and the court confirms a modification of the plan under section 1329 of this title.