The faint humming sound Tony gives in reply is undeniably pleased. Now they're definitely getting somewhere. Not that he can just leave it there.

"Just this? I don't know about that." Tony's smile flashes to something almost wicked for a second. "'Cause I have to tell you, I've had a few thoughts about your uniform and me on my knees."

Now this line of conversation is much more in Tony's comfort zone. Between that and the physical contact, he's lost any of the tension he might have had. But even though he's teasing, it doesn't mean he's not completely serious about it.