WASHINGTON (AP) — More than 130 lawmakers are urging the Obama administration to expand coverage for a lung-cancer test under Medicare that could cost the program billons.

In a letter to the Centers for Medicare and Medicaid Services, the lawmakers called for a timely decision on coverage for low-dose CT scans for older patients at higher risk of developing lung cancer.

A federal task force recommended the test for people ages 55 through 79 who smoked a pack of cigarettes a day for 30 years, amounting to about 10 million Americans. Private insurance will cover the CT scan under the Affordable Care Act with no copays, beginning Jan. 1.

But the health care law doesn't require Medicare to cover the screenings, which cost between $100 and $400. CMS is reviewing the proposal.