"I think this is a very important decision for all the people involved," Brawn told the official Formula 1 website in an interview.
"We won't be rushed on the decision and when the time is appropriate we will announce what we are going to do. I don't want to increase speculation by commenting on where we are."
Schumacher, whose contract with the team ends at the end of this year, is yet to decide if he will race on after his current deal expires.
The seven-time champion, who returned to the sport in 2010, has had a mixed season, with strong performances hindered by bad luck - though he was the fastest qualifier in Monaco and took the first podium of his comeback in Valencia.
So far he has scored just 29 points compared to team-mate Nico Rosberg's 77.
Brawn said it was the team's responsibility to take the blame for Schumacher's misfortunes.
"Well, you could argue what luck is," he said. "It was very unlucky for Michael - the problems that he had – but these problems have had a cause. There has been a reason why they've occurred, which has nothing to do with Michael.
"It just occurred on his car and you categorically can't see any reasons why they occurred on Michael's car, but they have.
"So the fact is that something went wrong – and when something goes wrong it's the responsibility of me and the team to not allow it to go wrong again. He had that many years perhaps benefiting from good fortune and this year he has some poor fortune, but I prefer not to believe in luck – not in motor racing."