In his soon-to-be published book The Keeper, Howard said that fellow American Friedel refused to endorse his work permit application in an attempt to "sabotage" his move to Manchester United from the New York MetroStars in 2003.
Howard said in his autobiography: "The legal team at Manchester United... told me that Brad hadn't merely refused to sign a statement on my behalf, he had actively tried to block my transfer.
"He'd written to the appeals committee suggesting that I shouldn't be given a work permit at all."
However, Friedel strongly hit back in an interview with ESPN FC on Wednesday.
The former United States international keeper quashed Howard's comments and said he wants an apology from the 35-year-old Everton shot-stopper.
"It's complete garbage," the 43-year-old said in a phone interview from England.
"To be honest with you, all we're looking for is an apology.
"We can't get the book reprinted. I'm not looking for monetary gain. I just want an apology.
"There is no letter. I never sabotaged and I never stood in the way of Tim Howard getting a work permit. This is ludicrous."
Friedel admitted that he did not sign Howard's work permit application as the letter was not accurate.
The Tottenham veteran said the application claimed that Howard was in direct competition with Friedel for the number one spot at international level, which was not the case.
"The letter was full of exaggerations that the people on the PFA [Professional Footballers Association] and appeals committee would have seen through," Friedel added.
"It said that I had been in direct competition with Tim Howard for the starting job on the US national team for the last two years, when anyone who follows soccer knew it was between Kasey [Keller] and I.
"Yes, I refused to sign that. We got the letter and said 'We have to change this, because this isn't true.
"We made our changes and sent it back. They didn't like what I was going to sign so they didn't use it. And that was the end of the matter."
