WASHINGTON (CNN) -- Sen. John McCain, R-Arizona, slammed fellow Republican presidential candidate Mitt Romney Monday, joking that maybe the former Massachusetts governor's solution to the immigration problem is "to get out his small varmint gun and drive those Guatemalans off his lawn."

Listen to McCain in his own words

McCain was referring to Romney's previous comments on what type of hunter he is and a report in The Boston Globe late last year that a landscaping company Romney hired employed illegal immigrants, at least one of which was from Guatemala.

McCain, also alluding to criticisms that Romney changes position depending on what is politically expedient, added that he'd "wait a couple of weeks and see if the winds change and Mitt comes back around." The Arizona senator's comments, confirmed by his presidential campaign, came during a conference call with conservative bloggers.

Kevin Madden, a Romney spokesman, fired back at McCain for criticizing the former governor.

"Governor Romney has been very clear that he opposes this immigration agreement, which clearly falls short of the American public's expectations," Madden said. "It seems that the candidate who brokered this flawed plan is having a very difficult time coming to terms with the political fallout that has ensued and cannot even muster up a substantive argument in favor of it."

-- CNN's Steve Brusk and Alexander Mooney