Zaheer, who took a career-best nine for 138 in a match against Essex, is still hoping to be called for the World Cup and the club is eagerly awaiting his reply in case the international plans do not work out.
''I think he has enjoyed every minute but quite understandably he has international ambitions. He wouldn't want to commit at this stage so it is an ongoing thing,'' Worcestershire chief executive Mark Newton was quoted by BBC Sport as saying.
''We will have to see if he gets picked for a one-day series in September with Australia and West Indies in Malaysia in terms of having a good idea of whether he is back in the fold or not,'' he added.
Mr Newton said the club was willing to wait for his reply as Worcs' were more then satisfied by the seamer's performance so far.
''In the end we will have to wait for that and then have a conversation about next season. He has produced the goods on the field and off the field he is a super bloke to deal with,'' he revealed.
''He is no hassle, he does the job and hasn't had any injury problems. What more do you want from an overseas player?,'' he added.