"He's not able to play," Guardiola told reporters, according to the Guardian. "I don't know (when he’ll be back)."
Ederson suffered a muscular injury during City's midweek draw with Atalanta in the Champions League. However, Guardiola expressed confidence in Claudio Bravo, who will start between the sticks.
"We have another top keeper," the manager said. "Claudio Bravo can do it (play out from the back) too. We won the Carabao Cup and FA Cup thanks to Claudio."
Bravo, who replaced Ederson at the San Siro on Wednesday, was later sent off in the match when he received a red card for a challenge on Josip Ilicic. City defender Kyle Walker was brought in to play goalkeeper for the final minutes of the 1-1 draw.
But Guardiola insisted that he trusts Bravo to perform well against a Liverpool team that owns a six-point edge over City after 11 games this season.
"Why shouldn’t I be confident about my players? I see him every day in training," Guardiola said of Bravo, according to BBC Sport's Simon Stone. "We won't lose because of Claudio. The red card the other day was because we lost the ball. Respect the guy. He is a top 'keeper."
Despite the possibility of City facing a nine-point deficit if Liverpool secure three points at home, Guardiola doesn't believe his team's hopes of defending the Premier League title would be over.
"I don’t know," he said. "In November it is never the end. The experience in the squad is to fight until the end … on Sunday and in the rest of the games. Liverpool lost only one game last season and none this season … but a lot of situations can happen."
City's visit to Anfield last season ended in a goalless draw before Guardiola's men claimed a 2-1 victory at the Etihad Stadium in their final encounter of the campaign.