The England forward, currently sidelined by a shoulder problem, is out of contract at the end of the season, and so could open talks with foreign clubs in January.
"Ideally he has to commit. It is difficult. I believe you have to commit at some stage," said the Arsenal manager.
Negotiations are continuing, with both sides aiming to reach an amicable compromise over terms.
Walcott, 23, used an article in Wednesday's programme notes for the Champions League game against Montpellier to stress he wanted to get "something sorted out", while adding "I don't think you can put a timeframe on when it will be resolved".
Wenger added: "It is very important in our sport to be very committed to where you are, and as long as you do not do that, you are not completely at ease.
"It is important for our squad as well that he is completely committed.
"I do not doubt it, but as well at some stage it has to be concrete."