Romney's former rival Rick Santorum to speak at Republican convention

U.S. Republican presidential candidate Mitt Romney shakes hands with supporters after a campaign event in Golden, Colorado August 2, 2012.

Wolfeboro, New Hampshire (Reuters) - Republican presidential candidate Mitt Romney's most bitter rival for his party's nomination has agreed to speak at the nominating convention in Tampa, Florida, later this month.

Rick Santorum, the former presidential candidate who lobbed harsh criticism at Romney during some bitter primary contests, will join a host of other big-name Republicans as headline speakers, according to Republican sources.

Former Florida Governor Jeb Bush will also speak at the convention, along with Oklahoma Governor Mary Fallin and Tea Party hero and Senator Rand Paul of Kentucky.

Paul spent much of the year campaigning against Romney on behalf of his father, Texas Congressman Ron Paul.

Details about when the speakers will take the stage have not been released.

After winning the Iowa caucuses, Santorum emerged as an unlikely but persistent burr in Romney's side, warning that the Republican Party would make a mistake by picking the former Massachusetts governor.

Because of that, some senior Romney advisers argued against giving Santorum, a former senator from Pennsylvania, a speaking slot at the convention, fearing he might go off-message and reprise some of his criticisms from the primaries.

Santorum announced he was suspending his campaign on April 10, clearing the way for Romney to begin campaigning in earnest against President Barack Obama.

Jeb Bush will not be joined by his brother, former President George W. Bush, who announced recently he will not attend the convention.

Romney will likely address the convention on Thursday, August 30 in a primetime address where he will formally accept the Republican nomination.

Speculation remains rampant over who Romney will choose to join him on the ticket as his running mate.

On Monday, the Republican candidate laughed off a question about whether he was meeting with potential candidates Tim Pawlenty, the former governor of Minnesota, or Senator Rob Portman of Ohio while spending some time off at his lake house in Wolfeboro, N.H.

(Reporting By Sam Youngman; Editing by Stacey Joyce)