Mayor Antonio Villaraigosa -- Charlie Sheen's Not My Bro ... It's Just a Picture

L.A. Mayor Antonio Villaraigosa is setting the record straight ... he's NOT BFFs with Charlie Sheen -- and he only posed for a pic with the actor because he's in the "picture taking business."

Mayor Villaraigosa went on NBC 4 L.A. on Saturday to explain the infamous "Cabo photo" -- showing him arm-and-arm with Sheen in Mexico, at the same hotel where Charlie dropped homophobic slurs.

The snapshot ignited a media frenzy and a wave of public backlash for the politician.

The mayor makes it clear in the interview he only met Sheen for a moment, saying, "I had a three-minute conversation and took a picture with him, that simple."

He explained further, "I take a picture virtually every single day, 50 times. And I took a picture with him ... I have never said no to anyone who wants to take a picture."