Forty-six-year-old four-time world champion Holyfield (42-9-2, 27 KOs) will square off with Valuev, 35, dubbed The Russian Giant (49-1, 34 KOs), on December 20 in Switzerland.
"Evander Holyfield is a very experienced fighter," Valuev told a joint news conference with Holyfield. "I have repeatedly said that I have no illusions about his age, and never underestimated him. I believe I have practiced enough to leave the ring as the winner."
If Holyfield, who lives and trains in Atlanta, Georgia, beats 7-foot (2.13-meter) Valuev, he will become the oldest ever heavyweight world champion.
Holyfield said he is convinced that neither his age nor Valuev's height and size will matter in the upcoming bout.
"I have been asked about my age so many times, but that is fine. It is not about how old you are... I am very experienced and I know what I have to do against Valuev," he said.
Holyfield, who is reportedly paying up to $500,000 a year in child support for nine of his 11 children from previous marriages, said earlier that he was planning to hang up his gloves in 2009 after the bout with Valuev, which he viewed as an additional source of income.
Valuev became Russia's first world heavyweight champion in December 2005 when he defeated John Ruiz. Last year he was just a few steps behind the record of legendary Rocky Marciano, who retired at 49-0 as boxing's only ever undefeated heavyweight champion, but lost his title bout to Ruslan "White Tyson" Chagaev of Uzbekistan, suffering the first and the only one as of today defeat.
Valuev and Chagaev later scheduled a rematch, which did not take place due to Chagaev's injury.
Chagaev, who is currently the WBA champion in recess, said in an interview with the FightNews.com website that he did not know who would win the Valuev-Holyfield bout, but said that Valuev was not a real WBA belt holder.
"This is not a real championship for me. I'm the champion because Valuev lost against me. He can't be a champion," Chagaev said.
The 30-year-old Uzbek boxer (24-0, 17KOs) will face on February 7 Puerto-Rican Carl Davis Drumond (26-0, 20 KOs) in Germany's Mecklenburg.
All four heavyweight championship titles currently belong to boxers from the former Soviet Union: Ukraine's Wladimir Klitschko holds the IBF and WBO titles, his older brother Vitali Klitschko holds the WBC belt, and Russia's Nikolai Valuev is the WBA champion.