Senator Scott Brown warily agreed on Monday to a debate co-sponsored by the Edward M. Kennedy Institute for the U.S. Senate, saying that he will only participate if he is confident that the event will be politically neutral.

In a letter to the EMK Institute, Brown asked that Victoria R. Kennedy, the wife of the late Senator Edward M. Kennedy ’54-’56 and the chairwoman EMK Institute, remain neutral and uninvolved in his current Senate race against Harvard Law School professor Elizabeth Warren.

“In order to proceed, we need to know that in keeping with the spirit of neutrality expressed in Vicki Kennedy’s letter that she will not endorse or otherwise get involved in this race,” Brown’s campaign manager Jim Barnett wrote in a letter to the EMK Institute.

The Republican campaign’s response comes a week after Kennedy sent letters to both campaigns inviting the candidates to a debate on September 26 co-sponsored by the EMK Institute and the University of Massachusetts Boston. Kennedy proposed that longtime NBC newsman Tom Brokaw would moderate a nationally televised debate on MSNBC.

Brown requested that MSNBC be replaced in favor of a local station.

“While we accept Tom Brokaw as a moderator, we prefer debates with local media sponsors, not out-of-state cable networks with a reputation for political advocacy,” Barnett wrote.

Though there has been some discussion surrounding the date of the debate, which is currently scheduled to be held on the Jewish High Holy Day of Yom Kippur, Warren accepted the invitation last Monday without conditions. She urged Brown to do the same in honor of the memory of the late Kennedy, who held the Senate seat for more than 40 years.

Brown’s campaign said at the time that the debate, like other invitations, was still under consideration. As Barnett expressed in his letter Monday, Brown was hesitant to accept a debate sponsored in part by a member of the powerful Massachusetts Democratic family, many of whose members have already endorsed Warren.

The candidates have had other difficulties agreeing about when and where they will debate since Warren became the official Democratic nominee earlier this month.

Both candidates have agreed to two yet-to-be-scheduled televised debates, one hosted by WBZ-TV of Boston and one by a consortium of out-of-state media outlets. Warren has committed to an additional televised debate and Brown to two radio debates.

In a press release Monday afternoon, the Massachusetts Democratic Party criticized Brown for his attempts to change the terms of the debate.

“Scott Brown is tying himself in knots over debates,” Massachusetts Democratic Party Chair John Walsh wrote in the release. “The junior senator just needs to sit down with the Warren folks and have an honest conversation. It's not that hard.”

Neither Warren's campaign nor the EMK Institute could be reached for comment.

—Staff writer Nicholas P. Fandos can be reached at nicholasfandos@college.harvard.edu.