WASHINGTON—Several of Republicans’ largest proposed spending cuts can’t be done in the fast-track budget process they are using to advance their megabill, the Senate parliamentarian ruled, dealing a significant blow to the GOP’s hopes of passing their plans quickly.

A new proposal to help stabilize rural hospital access is floating around Capitol Hill as Senate Republicans consider their reconciliation bill.

One key unsettled issue stalling progress on President Donald Trump's big bill in Congress is particularly daunting: How to cut billions from health care without harming Americans or the hospitals and others who provide care?