Since winning the Premier League title in May, Pellegrini has strengthened his squad with the acquisitions of Bacary Sagna, Fernando and Willy Caballero.
City have also long been linked with a move for Porto's Eliaquim Mangala and Pellegrini said the club remains eager to strengthen ahead of the new Premier League campaign.
Pellegrini's men begin their title defence against Newcastle United on August 17.
"I don't think the squad is complete yet but we have six weeks before the transfer window closes," said the Chilean.
"Perhaps there is the option to bring one or more players in, or maybe one or two will leave our squad but there is time for us to consider what is best for our team."
City's pre-season preparations, which began against Dundee last week, have been hampered by a foot injury suffered by striker Alvaro Negredo.
Pellegrini confirmed the former Sevilla man has been operated on and will likely miss up to three months of action.
"Alvaro had surgery today on his broken foot and he will probably be out for two or three months," he added.
"It is a blow for us because Alvaro is a very important member of our squad so obviously we will miss him."