Aguero, who has missed City's last five games with a hamstring problem, has scored 26 goals in 28 club appearances this season, while Premier League top scorer Suarez has netted 28 in 33 in all competitions.
"They are both top players," Pellegrini told reporters. "Suarez has had the whole season playing, he has scored a lot of goals and Sergio has had a difficult season with injuries, but I wouldn't swap.
"I think a lot of Suarez. He is a great player, not only a striker. He scores goals, but also plays a lot for the team.
"If you tell me I could change him for Sergio, no. I continue with Sergio."