At the risk of getting a slew of "not in my case" responses, when will both guys and girls understand that intergender friendships are never possible until intimacy has been resolved? Unless you have plans on sleeping with the guy, the answer is no.
Realistically, what degree of 'freindship' do you think you could ultimately have? In otherwords, honestly visualize what sort of frinedship you'd think would be ideal and ask yourself if you really think it's possible. In this instance I'd say definitely not. The guy want's to fvck you and not his wife, that sexual anxiety will always persist until one of you relents by either giving in to a made up 'accident' or you or he gives up in futility. Don't kid yourself, and don't play 'friends', you wont be in the end.
Follow this 'friendship' to it's logical conclusion, what would you do as 'friends'? Would you do the same things you do with your same sex friends, would he be doing the same things as well for his? Even in the best of circumstance intergender frienships are a farce until intimacy is resolved. Imagine you were the woman he's married to, would you think if went off to a movie or talked for any length of time with his 'woman friend' in favor of spending time with you that you could accept it as platonic? Women know this, and they're all too happy to entertain guy's stupid efforts to get into their pants when it serves their need for attention. That is until they're the ones in the LTR, then all that pretense they found so useful while single flys out the window, because she's used the same 'friendship' angle to keep more than a few fish on the stringer herself.