Sixteen patient and provider groups have opposed the latest healthcare plan put forward by Republican senators as a replacement for Obamacare.
In a joint statement, they said the proposal would endanger access to care for millions of Americans.
For years, Republicans have pushed to abolish President Barack Obama’s law, which expanded health insurance but failed to curb rising medical costs.
The bill will need 50 votes to pass the Senate before going to the House.
It would then go to the White House for the president’s signature.
Despite their longstanding opposition to Obamacare, Republicans have so far been unable to agree on a replacement.
Since taking control of the White House, several attempts to rally around a new plan have collapsed.
Now they have only until the end of the month to pass this bill.