GREENSBORO, North Carolina (Reuters) - A federal judge on Friday left the door open for former Democratic presidential candidate John Edwards to call two campaign finance experts to testify at his trial next month on charges of using illegal campaign funds to hide an extramarital affair.

Prosecutors wanted to block two former Federal Election Commission members from testifying that they believe Edwards acted within federal campaign finance laws.

Edwards, 58, is accused of secretly accepting more than $900,000 from two wealthy supporters to help cover up an extramarital affair and a child conceived with his former campaign videographer, knowing that those revelations would doom his campaign.

The money was given to an Edwards aide to pay for former videographer Rielle Hunter's medical visits, prenatal care, rent, car, air travel and other living expenses, according to the indictment.

Edwards, a former U.S. senator from North Carolina and John Kerry's vice presidential running mate, has pleaded not guilty to charges of conspiracy, taking illegal campaign contributions and making false statements. His trial is set for January in Greensboro, North Carolina.

If convicted, Edwards faces up to five years in prison and a $250,000 fine on each count.

Defense attorney Abbe Lowell argued the experts should be allowed to weigh in on whether Edwards' claim that he did not knowingly or willingly violate election laws was a reasonable mindset.

The defense contends the payments were intended to hide the affair from Edwards' wife, who died of breast cancer last year, and were not campaign contributions subject to campaign finance laws.

Prosecutors said the experts' opinions would usurp the roles of the judge and jury and should not be allowed. The government lawyers indicated they do not plan to call their own expert witnesses.

U.S. District Judge Catherine Eagles withheld making a definitive ruling until the trial on whether the former FEC commissioners will be permitted to testify and to what extent, noting prosecutors had made some legitimate points.

"I see some real issues about putting everything in that the defense is proposing," said Eagles, who in October denied Edwards' motions seeking to get the case dismissed.

The judge barred the defense team from referring to any of the experts' specific opinions in their opening statement at trial, but said "the government should be prepared for the possibility that I will let some of this expert testimony in."

(Editing by Greg McCune)

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