The Obama administration’s pay czar Kenneth Feinberg has vowed to keep pushing to lower hefty bonus payments being doled out by American International Group, Inc. — but says he’s constrained by promises the company made to employees several years ago.

“I am as troubled as Main Street is by the contracts,” Feinberg said in a Wednesday interview, referring to deals signed before the financial crisis that guaranteed millions in bonuses to executives in AIG’s Financial Products unit.