Umenyiora confirmed a report by the Newark Star-Ledger on Thursday night.
"We both decided he really wouldn't be able to help me out with this situation," Umenyiora said in an email response to ESPNNewYork.com. "I haven't hired a new agent, and I'm not really looking to hire a new agent."
Umenyiora has long been seeking a new contract extension from the Giants. He is entering the final year of his contract worth just under $4 million.
General manager Jerry Reese said the team has offered Umenyiora an extension the past two years but Umenyiora countered by saying the team has only offered a guarantee of half of the $10.95 million guaranteed money Mathias Kiwanuka received when he recently signed a three-year extension worth $21.75 million.
The defensive end has been looking to upgrade the seven-year, $41 million contract he signed in 2005.
Cole signed a four-year extension worth $48.525 million, including $15 million guaranteed. Mathis' new four-year extension is worth $36 million with $17 million guaranteed.
Both sides remain far apart from a resolution. Agnone could not be reached for comment.
Teammates like Kiwanuka have said that they understand Umenyiora's frustration with his contract.
"Osi is a very very critical and key part of our team and I'm just hoping that things work out," safety Antrel Rolle said on SiriusXM NFL Radio. "I truly do believe he deserves what he's asking for but, you know, that's not my decision to make and I don't get involved in any of that talk. Jerry Reese and Osi have a great relationship but business is business and sometimes business can get a little sticky. I think we all understand that."
Justin Tuck, who is close with Umenyiora, hopes both sides can come to a resolution.
"Osi's been a great part of our success here and I just feel as though he needs to be rewarded for that," Tuck said at his charity billiards event in Manhattan to benefit his R.U.S.H. for Literacy foundation. "Hopefully, the Giants can do that. But he understands the business and understands that Jerry Reese and our ownership is going to do everything in their power to put the best team forward. I'm not really picking sides. I'm just stating the obvious."