Karrueche Tran has vowed to stick by Chris Brown ''no matter what''.

The 25-year-old model is reportedly keen to reassure her on/off boyfriend - whose misdemeanour assault trial has been delayed until June 25 - that she will be there for him, even if he is sentenced to more jail time.

A source said: ''She wants to assure him that there's nothing to worry about and that she will be there for him no matter what, even if worse comes to worse.

''She feels like the beginning of his trial will be the biggest day of her life because Chris' fate is all on the line and [there] ain't s**t she can do.''

The 'Yeah 3x' hitmaker - who is currently in jail because his arrest for the alleged assault last October represented a violation of the terms of probation which was set following his assault on then-girlfriend Rihanna in 2009 - is said to have confided in Karrueche about how tough he is finding life in prison before his trial was postponed this week.

The source told HollywoodLife.com: ''Kae couldn't believe it because he's rarely ever emotional with her. He told her he's tired and that he couldn't sleep and how he doesn't know if he'll be able to fall asleep because he's nervous.

''He told her to keep her fingers crossed for him and keep good thoughts because he doesn't know what's going to happen.''

If convicted on the assault charge, the 'Run It' star faces a maximum of six months in jail and $1,000 fine, but he also faces up to four more years in jail in California as a result of violating the terms of his probation.