Justin Bieber wanted to `cool things down` with Sofia Richie?

Los Angeles: Pop star Justin Bieber called things off with model Sofia Richie because he reportedly wanted to slow things down.

The 22-year-old singer recently split from Richie, 18, after just a month of dating, but sources are now saying that the pair were "never officially together", and that the "Love Yourself" hitmaker decided to put an end to it because it was getting too "hot and heavy", reported E! Online.

"They were never officially together, but more casual hanging out and having fun. It was super hot and heavy, and because Justin doesn't want a relationship right now, he wanted to cool things down. It wasn't an intentional cool-off, it just sort of happened on its own."

The news of the "Sorry" musician's decision to call things off comes just days after Richie, who is the daughter of music legend Lionel Richie, opened up about their "special relationship".