... Jamaal Lascelles and Karl Darlow are set to sign for Newcastle.
The deal will see both players remain at the City Ground for the 2014/15 season as part of a loan arrangement between the two clubs.
United will pay a total of £5million for central defender Lascelles, 20, and goalkeeper Darlow, 23.
Pearce told the Nottingham Post: "We had an offer from Newcastle, that I was made aware of last week, in regards to the two players going there.
"The figures that were mentioned, by the representative of our club - I said I would not do that deal, when I was asked the question.
"I thought I could push their value up and that they would be worth more in the long run.
"The first I heard today about things was when Jamaal Lascelles came in and told me that he had a medical at 2pm at Newcastle.
"That disappointed me greatly."
Darlow joined Forest in 2006 after being released by Aston Villa's academy as a teenager.