Brown is confident top-order batsman Will Porterfield will put pen to paper on the new deal on offer to him from the Bears and that would leave former Surrey player Clarke as the only senior player out of contract at the end of the 2013 campaign.
Clarke, who has played in two Tests and 20 ODIs for England, is currently part of the Lions squad touring Australia and Brown wants to open talks when he returns.
Brown said: "A new contract is there waiting for Will to sign and I don't see any problems.
"He has been working on some technical points with his batting this winter and I think people will see an improvement when the season starts.
"Rikki is also a crucial member of the squad and we would be delighted if he signed an extension.
"While he is in Australia with the England Lions, he will be concentrating on that.
"But it (the new contract) is something we will be looking to get on to straight after he gets back."
Clarke joined the Bears from Derbyshire four years ago and was part of their 2012 LV County Championship-winning side.
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