One of the nation’s largest senior advocacy groups is warning lawmakers of the “lasting impact” of Medicare cuts that would be potentially included in the GOP’s final tax reform bill.

Provider and consumer groups alike have expressed concerns over the possibility that the bill becoming law could trigger “automatic” Medicare cuts under what’s known as the “pay-as-you-go” or PAYGO rule. That rule could result in a $25 billion cut from Medicare in fiscal year 2018 alone, which would be used to offset the debt incurred by the legislation.

The Senate version of the bill was passed earlier this month. That version will now have to be reconciled with the House version, which was approved in November.

In a letter to House and Senate leaders sent Thursday AARP CEO Jo Ann Jenkins warned that any cuts to the Medicare program could lead healthcare providers to stop accepting beneficiaries, despite the 10,000 seniors that enroll in the program each day.

“The sudden cut to Medicare provider funding in 2018 would have an immediate and lasting impact, including fewer providers participating in Medicare and reduced access to care for Medicare beneficiaries,” Jenkins wrote.

She also told Congressional leaders many had made promises to make sure the bill doesn’t trigger the cuts. Both Senate Majority Leader Mitch McConnell (R-KY) and House Speaker Paul Ryan (R-WI) have indicated that Congress would waive the PAYGO rule.

“I can’t imagine any scenario where there’s not a waiver for PAYGO,” Rep. Mark Meadows (R-NC) told reporters on Wednesday. “It’s using a hammer when maybe a scalpel would do. So I don’t see that, even among conservatives, being supported. A waiver ultimately will happen.”