(CNN) - A top adviser to Mitt Romney's presidential campaign said Monday that Rep. Paul Ryan's Medicare plan is on the backburner now that he is Romney's running mate.
"The plan that this ticket will be supporting is the Romney plan, and the Romney plan has slight differences with the Ryan plan," former New Hampshire Gov. John Sununu, a high profile Romney surrogate, told CNN's "The Situation Room with Wolf Blitzer."
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"Romney's positions become Ryan's (positions)," Sununu said.
Ryan's new spot as Romney's vice presidential candidate has brought renewed scrutiny to both Republicans' Medicare proposals.
At a press conference in Miami on Monday afternoon, Romney declined to say where their differences lie.
"We haven't gone through piece by piece and said 'oh, here's a place where there's a difference,' " Romney said. "I can't imagine any two people even in the same party who have exactly the same positions on all issues, but my plan for Medicare is very similar to his plan for Medicare."
Sununu told CNN: "The principle difference is not only does the Romney plan guarantee that anyone 55 and older will not have their Medicare touched, but it provides some options for them, for those under 55 that are slightly different."
He did not go into what those options would be.
Sununu insisted that Romney and Ryan "don't disagree" on the Medicare issue.
Asked if that meant Ryan was "abandoning" his own plan, Sununu replied: "He didn't abandon it - you have a top of the ticket. The top of the ticket is running for president. Presidents make decisions."
- CNN's Gregory Wallace and Rachel Streitfeld contributed to this report