Except as provided in subsection (c) of this section, the Secretary of the Treasury may require an employer maintaining a defined benefit plan which is a single-employer plan (within the meaning of section 1301 (a)(15) of this title) to provide security to such plan as a condition for granting or modifying a waiver under section 1083 of this title or an extension under section 1084 of this title.

Any security provided under paragraph (1) may be perfected and enforced only by the Pension Benefit Guaranty Corporation or, at the direction of the Corporation, by a contributing sponsor (within the meaning of section 1301 (a)(13) of this title) or a member of such sponsor’s controlled group (within the meaning of section 1301 (a)(14) of this title).

The preceding provisions of this section shall not apply to any plan with respect to which the sum of—

For purposes of paragraph (1)(A), accumulated funding deficiencies shall include any increase in such amount which would result if all applications for waivers of the minimum funding standard under section 1083 of this title or section 412 (d) of title 26 and for extensions of the amortization period under section 1084 of this title or section 412 (e) of title 26 which are pending with respect to such plan were denied.