By Sam Youngman

Wolfeboro, New Hampshire Aug 6 (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, Aug. 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.

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  • Jan. 10, 2012 -- "That Smell"

    At a campaign stop in New Hampshire, Romney dodged the <a href="http://www.huffingtonpost.com/2012/01/10/mitt-romney-marijuana_n_1197619.html" target="_hplink">medical marijuana</a> issue. "It's a long ... it's a long question," he told a member of Students for Sensible Drug Policy. "It deserves a full answer, and not just in a photo line like this." (EMMANUEL DUNAND/AFP/Getty Images)

  • Jan. 24, 2012 -- "Still Unbroken"

    Romney <a href="http://www.huffingtonpost.com/2012/01/24/mitt-romney-tax-returns-released_n_1225247.html" target="_hplink">released his tax records</a>, showing that he and his wife, Ann, paid a 2010 rate of 13.9 percent. Thanks to a large portion of his earnings stemming from capital gains and investments, that amount was below what most Americans paid. (EMMANUEL DUNAND/AFP/Getty Images)

  • Feb. 1, 2012 -- "The Ballad Of Curtis Loew"

    In an interview with CNN, <a href="http://www.huffingtonpost.com/2012/02/01/mitt-romney-very-poor_n_1246557.html" target="_hplink">Romney told viewers</a> that he's "not concerned about the very poor," explaining that there is a social safety net in place for that part of the population.

  • March 7, 2012 -- "Tuesday's Gone"

    Romney fell short of breaking away from the GOP field on <a href="http://www.huffingtonpost.com/2012/03/07/mitt-romney-results-super-tuesday-2012_n_1318741.html" target="_hplink">Super Tuesday</a>. Even with a narrow win in Ohio and a host of losses in other states, optimism was abound. "There will be good days and bad days, always long hours and never enough time," he said during his speech. "But, on November 6th, we will stand united -- not only having won an election, but having saved a future." (Win McNamee/Getty Images)

  • March 12, 2012 -- "What's Your Name?"

    In an attempt to reach out to Southern voters, Romney mixed <a href="http://www.huffingtonpost.com/2012/03/12/mitt-romney-hugs-southern-girls-mobile-alabama_n_1339692.html" target="_hplink">age, women and hugs all in one</a>. At a campaign rally in Mobile, Alabama, he emphasized his desire to have female voters embrace his White House run. "Please give us a big hug, that's the girls," Romney said. "I've been getting hugs from the Southern girls ... from 12, to well, a lot more than 12." (Win McNamee/Getty Images)

  • March 12, 2012 -- "Sweet Home Alabama"

    Rain or shine, <a href="http://www.huffingtonpost.com/2012/03/12/mitt-romney-alabama-sardines_n_1339265.html" target="_hplink">Romney has his way with words</a>. At a stormy campaign event in Alabama, Mitt and his ralliers huddled under a restaurant overhang to escape the inclement weather. "Look at us in here," Romney remarked. "We are all nice together, all nice and wet, you know, like a can of sardines." (Win McNamee/Getty Images)

  • April 13, 2012 -- "God & Guns"

    Speaking at an <a href="http://www.huffingtonpost.com/2012/04/13/mitt-romney-nra-beware_n_1424081.html" target="_hplink">NRA convention</a> in St. Louis, Romney warned that reelecting President Barack Obama would lead to an "unrestrained" assault on freedom. He enforced his pro-gun stance at the event, telling listeners that "the right to bear arms is so plainly stated, so unambiguous, that liberals have a hard time challenging it directly. Instead, they've been employing every imaginable ploy to restrict it." (KAREN BLEIER/AFP/Getty Images)

  • April 15, 2012 -- "Simple Man"

    MSNBC's "Up w/ Chris Hayes" unearthed a controversial January 2012 comment from Romney on moms and work. The GOP hopeful told a Manchester, N.H., audience that poor <a href="http://www.huffingtonpost.com/2012/04/15/mitt-romney-mothers-welfare-moms_n_1426113.html" target="_hplink">stay-at-home mothers</a> should be given federal assistance so they can get jobs and "have the dignity of work." This news arrived days after his anger at Democratic strategist Hilary Rosen's criticism of Ann Romney not working "a day in her life." (EMMANUEL DUNAND/AFP/Getty Images)

  • May 29, 2012 -- "Free Bird"

    Romney <a href="http://www.huffingtonpost.com/2012/05/29/mitt-romney-republican-nomination_n_1554534.html" target="_hplink">clinched the GOP nomination</a>, soaring past the required 1,144 delegates with a Texas primary win. "We did it!" he said in a message to supporters, adding that "it's only the beginning." (Photo by Justin Sullivan/Getty Images)

  • June 13, 2012 -- "Gimme Three Steps"

    Reporters were kicked out of a <a href="http://www.huffingtonpost.com/2012/06/14/reporters-mitt-romney-reporters_n_1596650.html" target="_hplink">Romney event at the Newseum</a> in Washington D.C. One of the press members on hand said that Mitt stayed to take questions, but the media was escorted out before being able to hear any answers. (Photo by Chip Somodevilla/Getty Images)