The world championship leader told Famiglia Cristiana magazine, which released an advance copy of the interview yesterday, that his future at Ferrari depended on the status of his team-mate.
"It depends. If Schumacher doesn't come back in the same role, then maybe," he said when asked whether he would be staying on next season. "But if he's the No 1 driver again I'm leaving."
Irvine has emerged from Schumacher's shadow by winning two consecutive grands prix since the German crashed and broke his leg at Silverstone last month. The Ulsterman has now won three races this season and heads the title standings by eight points from the defending champion, Mika Hakkinen of Finland.
Schumacher is not expected to race again until the Italian Grand Prix on 12 September and is virtually out of contention, already 20 points behind Irvine. The German, who is under contract at Ferrari until 2002, has said he will support Irvine in his campaign for the title once he returns, but Ferrari have not said who will be their No 1 driver next season.
Irvine said that Schumacher, the double world champion, was the fastest driver but not necessarily the best. "He's the fastest. With equal cars no one can beat him," Irvine told Italy's biggest circulation weekly magazine in the interview due to be published on Sunday.
"Speed is not enough. You need to avoid mistakes and he makes a lot. Too many," Irvine was quoted as saying. "This year we've... been lucky, the car is reliable and we're in front."
"I'm 33 and I don't plan to retire before I'm 36," Irvine said. "I love my work and I've already won three grands prix, just like John Surtees." Surtees won four races for Ferrari, the Englishman becoming world champion in the final race of 1964 in Mexico.