Justin Bieber is eager to rekindle his relationship with Selena Gomez and a source revealed that the "Boyfriend" singer will not back down until Gomez takes him back. 

The couple, who has been dating on and off for at least two years, recently traveled to Mexico together to celebrate New Year's but a fight allegedly broke out on Dec. 30, and they flew back home separately. Bieber was spotted leaving a Four Seasons hotel alone on New Year's Day and Gomez reportedly never stayed at the hotel.

Perhaps a nod to her being newly single, Gomez tweeted on Jan. 1, "New beginnings. Fresh start. I love you all." 

However, a source told HollywoodLife.com that Bieber, 18, is now desperate for Gomez, 20, to forgive him.

"Justin is calling her 100 times a day and she's not picking up," the source said.

Rumors have surfaced about the reason behind the Mexico fight. A different source confirmed that the couple has had trust issues in the past, with Gomez not liking who Bieber has been talking to and spending time with. 

"The problem in the first place is that Selena was a little bit of a jealous girlfriend and Justin wasn't really taking her feelings into regard," a source close to the singers told Radar Online. "Justin doesn't see texting other girls as cheating, but he's promised Selena he'll stop if she takes him back."

Back in Decemeber, a source "VERY close to Selena" said Gomez decided the end her relationship with the Canadian singer at one point because of her ex-boyfriend Nick Jonas and his friendship with Bieber.

Bieber tweeted that he won several pingpong games while hanging out with Nick Jonas, who then replied, "Just played #Justin Bieber in ping pong. Went to deuce both times, but he's the ping pong champion.

"She doesn't want to speak to him anymore and told him it's over," the source said. "Hanging out with Nick proved that he wants to just be a jerk about this, and Selena's sick of being heartbroken."

Tags: Selena Gomez Justin Bieber Nick Jonas