(CNN) -- Attorneys for John Edwards asked again Thursday to delay his criminal trial, saying the former presidential candidate and U.S. senator has an unspecified medical issue.
In June, the Justice Department charged Edwards with conspiracy, issuing false statements and violating campaign contribution laws. He has pleaded not guilty.
In September, the trial was delayed until January 30 after Edwards' attorneys said he needed more time, in part due to his position as the sole caretaker of his two youngest children, ages 11 and 13, after his wife, Elizabeth, passed away in December 2010.
The motion to continue the trial for 60 days filed Thursday says Edwards' "unexpected" medical issue is explained in a sealed exhibit. The issue will "prevent a trial of this matter during the January 2012 criminal term," according to the motion, and cannot be resolved before the end of the term.
Attorneys for Edwards, who was the Democratic vice-presidential nominee in 2004 alongside John Kerry, also say in the motion a January trial would not give them enough time to prepare, especially given the "unusual and complex" prosecution.
"Since this trial date was set, the government has produced as part of the discovery process an additional 103,102 pages of material including more than 91,000 e-mails as well as 26 voice mails received by cooperating witnesses between 2007 and 2010," the motion says. In addition, both the government and Edwards are seeking evidence from North Carolina state courts.
"Absent a continuance, Mr. Edwards' counsel will not be able to effectively use the evidence the government was obligated to provide him ... and this, in turn, threatens Mr. Edwards' right to effective counsel and a fair trial," according to the motion.
"This is not hyperbole. Mr. Edwards' counsel are experienced trial lawyers and they are and have been working hard -- long hours, late nights and weekends -- and they have not made it their practice to seek unwarranted continuances."
A chief issue in the upcoming trial is whether money given to support Edwards' mistress, Rielle Hunter, by the then-candidate's benefactors should have been considered campaign donations, a contention Edwards' team has disputed. They maintain the money was a gift to Hunter.
If convicted on all counts, Edwards could face 30 years in prison and a fine of up to $1.5 million.