In a stinging defeat for President Joe Biden, the Supreme Court blocked the administration's student loan forgiveness plan Friday, rejecting a program aimed at delivering up to $20,000 of relief to millions of borrowers struggling with outstanding debt.

The decision was 6-3 with Chief Justice John Roberts writing for the conservative supermajority.

Republican-led states and conservatives challenging the program say it amounts to an unlawful attempt to erase an estimated $430 billion of federal student loan debt under the guise of the pandemic.

Roberts said the Biden administration and Secretary of Education rewrote the law.

"The Secretary's comprehensive debt cancellation plan cannot fairly be called a waiver -- it not only nullifies existing provisions, but augments and expands them dramatically," Roberts wrote. "However broad the meaning of 'waive or modify,' that language cannot authorize the kind of exhaustive rewriting of the statute that has taken place here."

This story is breaking and will be updated.