WASHINGTON (AP) - President Barack Obama's health secretary told Congress Tuesday that there is no administrative action that would fix the "massive damage to our health care system" that would result should the Supreme Court invalidate federal subsidies that help millions of Americans buy health care coverage.

WASHINGTON (AP) President Barack Obama's health secretary told Congress Tuesday that there is no administrative action that would fix the "massive damage to our health care system" that would result should the Supreme Court invalidate federal subsidies that help millions of Americans buy health care coverage.

The letter from Health and Human Services Secretary Sylvia M. Burwell continued the administration's tough stance in its building confrontation with Republican lawmakers in advance of an expected Supreme Court decision in June.

In that case, conservatives and Republicans argue that Obama's 2010 health care law only provides government subsidies for people buying health coverage through marketplaces established by the states. Just 13 states established their own marketplaces, while the remaining 37 use the federal government's HealthCare.gov.

If the plaintiffs win, the 8.6 million people who have enrolled this year for policies through HealthCare.gov could not get subsidies.

In her letter to Senate Finance Committee Chairman Orrin Hatch, R-Utah, Burwell reiterated her warnings that a victory for the plaintiffs would cause millions to lose health coverage because they could no longer afford it.

That, in turn, would mean that disproportionately high numbers of sick, lower-earning people would continue buying health coverage, driving up health insurance costs for everyone else.

"We know of no administrative actions that could, and therefore we have no plans that would, undo the massive damage to our health care system that would be caused by an adverse decision," Burwell wrote.

For months, Burwell and other administration officials have angered GOP lawmakers by stating they have taken no steps in preparation for a Supreme Court victory by the plaintiffs.

"By admitting they have no contingency plan to assist the millions that may lose subsidies, the administration confirms how the misguided law is unworkable for the American people," Hatch said in a written statement.