More than 4 million borrowers are enrolled in the program, according to the Education Department, and the Biden administration has launched a public outreach campaign to get more Americans to sign up.

But Republicans have blasted the new repayment plan as a backdoor loan forgiveness program that provides wasteful subsidies to millions of borrowers at taxpayers’ expense.

The Biden administration estimated that its new plan would cost $156 billion over the next decade. The Congressional Budget Office previously pegged the figure at $230 billion, and outside analysts, such as Penn Wharton Budget Model, have said it could be as high as $475 billion.

GOP lawmakers are seeking to nullify the repayment plan under the Congressional Review Act, a tool that allows lawmakers to swiftly overturn recently enacted executive branch policies. It will allow Republicans to force a vote on the measure in the Democratic-controlled Senate.

A similar GOP-led effort to repeal Biden’s student debt relief program earlier this year, before the Supreme Court struck it down, passed Congress with a handful of Democratic votes, though Biden swiftly vetoed the measure.