My wife and I are best friends, however we fuck and that (I assume) is not what the question is about.
I used to believe you could, and have been in several friendships with various women in my time but am comfortable enough to admit that some I entered into knowing I fancied them, others knowing they fancied me and a couple knowing we both fancied each other, where circumstances and/or social norms meant we could not or should not allow things to develop sexually. Was even mates with a lad who told my now wife that he reckoned he could "turn" me.
All have one thing in common, we're no longer friends.
To me true friendship is being able to pick up the phone or turn up on their door step and vice versa and expect to give or receive help no questions asked. Difficult to achieve if one or more wants more out of the relationship (sexually) that the other, given the obvious resultant power imbalance.