Former Massachusetts Gov. Mitt Romney (R) won't participate in a GOP presidential candidate debate set for Thursday, the first of the 2012 cycle.

Romney, a putative front-runner for the party's nomination, won't participate in the debate in South Carolina because of its early position in the cycle, according to top aide Matt Rhoades.

"Gov. Romney will not be participating in this week’s South Carolina debate because it’s still early, the field is too unsettled and he’s not yet an announced candidate," said Rhoades. "Fox News and the South Carolina Republican Party have both been notified of this decision."

Romney's decision not to participate means that Thursday's debate, which will be co-hosted by the South Carolina GOP and Fox News, will be without some of the major figures in the 2012 race. Former House Speaker Newt Gingrich (R) has declined to participate, and other figures — including former Arkansas Gov. Mike Huckabee and former Alaska Gov. Sarah Palin — are ineligible to participate because of the forum's rules.

By contrast, former Minnesota Gov. Tim Pawlenty (R) has joined several other Republicans — Rep. Ron Paul (Texas), former Sen. Rick Santorum (Pa.), former Louisiana Gov. Buddy Roemer and pizza magnate Herman Cain — in committing to the debate.

Pawlenty pressured other Republicans to join in the forum, which follows an informal gathering last week in New Hampshire. (Romney participated in that candidate forum, hosted by Americans for Prosperity.)

"Well, I hope all of the serious or even potential candidates are going to get in this debate because — look, this is a president who’s got his challenges but he’s going to raise a billion dollars; he’s a very gifted campaigner and we’ve got to start taking the case to the American people why he should be fired," Pawlenty said.

Rhoades said Romney will next be in South Carolina May 21, and would be happy to debate in the Palmetto State as its primary next year draws nearer.