Ah, but they are still spending time on you, being there in your face. If they truly weren't interested in you, then they'd leave in search of easier prey.

Since your leaving could be spun as felony (in at least some jurisdictions) fleeing the police, you'd best not leave without their OK, explicit, or implicit by their leaving first.

Note: don't let yourself get startled by the police into running away. One of the things that reified all I've been reading about the modern police in the last decade or so was retiring and returning to my home town, and one day in 2007-8 a new, improved policeman played a game of chicken with my body and his car, that is, as soon as he noticed me, he veered it on a near collision course. I was an experienced enough pedestrian---which I think is unusual here---that I could tell his vehicle would miss me by a good foot or more and the mirror by at least half that, so I stared him down, and he then veered away. Based on my readings, I have have to assume he was trying to get me to run ("this crazy cop is trying to kill me!"), at which point the crime of fleeing the police could be claimed.