The Red Devils were said to be in negotiations with the Basque club after agreeing to meet his £31m release clause, only for it later to be revealed that three 'impostors' were falsely representing the Premier League champions.
Reports in Spain suggest that Leones fans may not take kindly to Herrera's apparent willingness to leave San Mames for Old Trafford, but the 24-year-old said that he remains committed to the cause.
"The only option, as the president said, was to pay my clause," Herrera told reporters. "I was never told United would pay the clause. At no time have either I or my agent reached an agreement with United.
"I've been silent because the important thing was [Sunday's] game at Real Madrid. Today I'm here, with no problem, with the truth. I will continue to demonstrate my commitment to the club as I have since the first day I arrived.
"I speak for me. I do not speak of other cases. The club can confirm that my behaviour has been fantastic. I'm very flattered to see that one of the biggest clubs in the world, such as United, bid for me [but] I did not talk at any time with United. I've been very quiet."
The Spanish Under-21 international joined Bilbao from Real Zaragoza two years ago.