Sen. Susan Collins Susan Margaret CollinsSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (R-Maine) said on Sunday that she has not yet made a decision on the GOP's tax-reform plan after saying last week she would consider changing her vote if her proposed amendments were not included.

“There are major differences between the House and Senate bills. I don’t know where the bill is going to come out," Collins told CBS News's John Dickerson on "Face the Nation."

"I also obviously care very much about amendments that I was successful in getting in the bill that particularly helps middle-income families," she continued.

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Collins said she was confident in an agreement reached with Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Senate GOP aims to confirm Trump court pick by Oct. 29: report Trump argues full Supreme Court needed to settle potential election disputes MORE (R-Ky.) and House Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) on Medicare.

"I have written correspondence that memorializes the agreement that the 4 percent cut in Medicare that could go into effect will not go into effect," she said.

"I don't want seniors to have the anxiety of wondering whether the tax bill is going to trigger a cut in Medicare. I am absolutely confident. I have it in writing, a statement by both Mitch McConnell and Speaker Ryan."

Collins said on Friday that she could change her vote on the tax legislation.

"I would [consider changing my vote]," she told a CBS affiliate in Maine.

"I'm going to look at what comes out of the conference committee meeting to reconcile the differences between the Senate and House bill. So I won't make a final decision until I see what that package is."