BOSTON (AP) - Mitt Romney has tapped a longtime adviser to begin his search for a vice presidential candidate.

Romney said Monday that campaign adviser Beth Myers is in charge of "selection and vetting and analysis."

Myers was Romney's chief of staff when he was governor of Massachusetts and she's a senior adviser on his presidential campaign. Romney is moving forward as the presumptive Republican presidential nominee after rival Rick Santorum suspended his campaign last week.

When asked during an interview with Diane Sawyer of ABC News about Florida Sen. Marco Rubio, Romney said it's "way too early" to start talking about prospective running mates. He says he has a deadline in mind for finalizing his pick but he declined to disclose it.

Romney spoke outside of Fenway Park in Boston.