Bachmann undecided on Trump debate, says 'questions' need to be answered

"We haven't made up our mind. There' a lot of questions on this," Bachmann said on Fox News's "Fox and Friends" Thursday. "I like Donald Trump a lot. We have a very good relationship, but there's a couple of issues behind the scenes."

Bachmann told Fox News that she is concerned about Trump's role as a moderator because he considered entering the presidential race as an independent and he plans to endorse one of the Republican candidates.

"Even if he's leaning towards me, it suggests the idea of bias and I just don't know if that's the right format," she added.

Thus far, only Newt Gingrich and Rick Santorum have agreed to participate.

The debate has drawn attacks from political pundits and some of the Republican candidates over Trump's involvement.

Ron Paul and Jon Huntsman declined to participate last week after it was announced Trump would be the moderator.

“The selection of a reality television personality to host a presidential debate that voters nationwide will be watching is beneath the office of the presidency and flies in the face of that office’s history and dignity,” Paul's campaign chairman, Jesse Benton, said.

Mitt Romney said Tuesday he could not participate because of a scheduling conflict.

Rick Perry turned down the debate opportunity Thursday, citing “retail campaigning” in the days leading up to the Iowa caucuses as his “top priority.”

Republican National Committee Chairman Reince Priebus advised presidential candidates against participating in the debate Thursday but couched his warning with strong praise for the influential Republican businessman.

“First of all, candidates can do whatever they want to do,” Priebus said Thursday on “Fox and Friends,” noting that he can’t bar candidates from participating in the debate if they so choose.

Trump, the host of NBC's reality show "The Apprentice," considered entering the GOP primary field earlier this year, but ruled out a bid in May, citing a passion for business over politics. Since getting out of the race, Trump has maintained a strong presence in the primary process, meeting privately with many of the candidates.