Celtic "are working really hard" for an "important" January transfer window, says manager Brendan Rodgers.

The Scottish Premiership champions sold Moussa Dembele and Stuart Armstrong in the summer, bringing in Odsonne Edouard on a permanent deal for a record £9m.

Rodgers admits he "did not hide a natural frustration very well" as other signing targets were missed.

"We're assessing targets and the areas we need to strengthen in and improve," said Rodgers.

"January is an important window. That's an ongoing matter. I'm sure there will be enough talk in January about that. In the meantime, the focus is on the players that are here.

"The guys behind the scenes are working really hard, preparing for some players to come in."

'You won't always agree but there's respect'

In August, Celtic failed to reach the Champions League group stage for the first time in three seasons under Rodgers.

Following the qualifying defeat to AEK Athens, the manager said "it's not rocket science" to say Celtic should have been busier in the transfer market.

"I'm not one that can hide it very well, I wasn't hiding it very well at all," said Rodgers.

"There was a natural frustration because as a manager and leader of the team, you want to continue pushing forward.

"But you come away and review and reflect. What's great about my relationship with the board is that, when you work so closely together, it's only human that you won't always agree.

"If you work closely with people you're not always going to agree. What there is between us all is a huge respect."

The Celtic manager added: "There's be an incredible collective effort on and off the pitch from us to be where we are now as a club. That has to be sustained and the way you do that is by communicating and talking and planning forward.

"So yes, it was a frustrating period but gradually we've worked our way through it and now come out the other end in a good position. But, of course, it's constant and in January we hope that we can improve the squad."

'Of course we want Scott to stay'

Rodgers went on to reiterate that captain Scott Brown "deserves time" to consider his future beyond the end of the season.

The 33-year-old midfielder is back in training after injury and has been linked with moves to Australia and the United States.

"He loves it here and there will be an agreement between him and the club in relation to that," said Rodgers.

"If he has options in this last period of his career, then he probably needs time to look at that. But that shouldn't be taken by any Celtic supporters that he doesn't want to be here. He's been absolutely top class for me and we want him to stay of course."