Iwelumo will be available to face Doncaster, Crystal Palace and Reading before his stint at Ashton Gate expires.
Johnson told the club's official website: "We'd like to keep Chris for another month. I speak to Mick McCarthy (Wolves boss) after every couple of games to let him know how Chris is doing.
"Wolves are in no doubt about our desire to keep him for another month and now it's in their hands.
"It was always going to be a month-to-month loan. He's still got three games left and we'll keep the dialogue going with Wolves. He's a great lad to have around the club, on and off the field."