In light of a meeting of the board at Mercedes on Wednesday, speculation had surfaced that an announcement regarding the team's driver line-up for next season was imminent.
Mercedes are known to have courted Lewis Hamilton, offering a deal to lure the 27-year-old away from McLaren.
The Woking-based marque, where Hamilton has spent the last 14 years, initially offered a deal slashing his current salary by a third.
It is believed that in a bid to keep Hamilton, McLaren have increased their contract offer by a further £2million to match Mercedes.
However, there has been no word from Mercedes, and unlikely to be for another few weeks at least, according to Brawn, as talks continue with 43-year-old Schumacher over his future.
"It's still under discussion, I'm afraid," said Brawn on BBC Radio 5 Live.
"I can't comment very much on that, but Michael's been a huge asset to the team, he's really taken us forward.
"I do think Michael contributes an awful lot, so I think the decision for Michael to stay or not continue is a difficult one.
"Obviously he's very involved in that decision, and discussions are ongoing at the moment."
Asked whether Hamilton could be joining Mercedes, Brawn naturally ducked the issue, adding: "I think any ambitious team looks at the top drivers and we're an ambitious team.
"But I think there's an awful lot of speculation. We will have some things to say in the next few weeks, next few months, and then all will become clear."