West Ham have strengthened with five new players including striker Javier Hernandez, defender Pablo Zabaleta and winger Marko Arnautovic but there has been speculation Argentine Manuel Lanzini was being lined up by Liverpool.
"We will see what happens in the last week of the transfer window, if somebody is going to leave or come in," Bilic told reporters ahead of Wednesday's League Cup match against Cheltenham Town.
"I'm happy with the squad now. I would like to have one more and after that, if somebody leaves we have to fill that gap because we don't have a big squad... We are happy but if somebody leaves we have to be ready to act."
West Ham, who have lost their opening two league games of the new season, travel to Newcastle United when Premier League action resumes on Saturday.