In a Shonen Jump (the publishers of Naruto) interview with Kishimoto (the manga-ka of Naruto)---
Shonen Jump Question:
Naruto and Sasuke kiss (accidentally) in the first chapter where they appear together. Does this add a special dimension to their rivalry?
Masashi Kishimoto Answer:
I didn’t have any particular reason for it, other then to surprise readers. I mainly did it because I don’t think there has ever been a manga where two rivals kissed. Also, by having this encounter, it was easier to set up the love triangle: Sakura, who had intended to be the first one to kiss Sasuke, has it stolen by her rival Naruto, Sasuke and Naruto are rivals, so there’s and added tension there. And so on and so forth.
If one would look closely to Kishimoto said, then he'll notice that he said that Naruto was Sakura's rival (in love?). Which means that Sakura somewhat sees Naruto as a threat in her quest for Sasuke's affection. Plus, he said that it was a love triangle. Obviously it would be that: Naruto likes Sakura; Sakura likes Sasuke; and Sasuke likes...Naruto? That would be the most obvious answer.