R&B singer Chris Brown's assault trial has been put on hold for months after prosecutors refused to grant immunity to his bodyguard, who would be a key witness in the case.

Brown, 24, will remain in custody for the near future after a Los Angeles judge denied a request by the Grammy-winning singer's lawyer to release him while he awaited trial.

His trial had been set to start in Washington DC yesterday and his bodyguard Christopher Hollosy had been expected to give evidence saying that he, not Brown, hit a man outside a hotel in the US capital in October.

Hollosy was tried separately and convicted of assault on Monday, but he plans to appeal. His lawyer has said that unless Hollosy is granted immunity, he will not give evidence until his appeal is over.

A lawyer for Brown said in court yesterday that it could take at least six months and prosecutors have said it could take a year. No new trial date for Brown was set.

Prosecutors told the judge they decided not to grant Hollosy immunity because he refused to meet them to discuss his evidence following his conviction. They also believe his likely evidence - that he alone threw a punch - would be a lie.

Prosecutors say Brown and Hollosy hit 20-year-old Parker Adams after Mr Adams tried to get into a photo Brown was taking with two women outside his tour bus. Witnesses told Hollosy's trial that Adams and Brown exchanged words over the picture and Brown, then Hollosy, hit Mr Adams.

Hollosy told police a different story, saying he hit Mr Adams after Mr Adams tried to get on Brown's tour bus. Brown denied hitting Mr Adams and made a similar statement to police.

A judge trying Hollosy's case found Hollosy struck Mr Adams and that Brown acted as the initial aggressor. A Los Angeles prosecutor cited the finding during a hearing yesterday, but it was not considered by the judge who refused to release Brown.

Earlier, DC Superior Court Judge Franklin Burgess set a status hearing in Brown's case for June 25, the same day Hollosy is due to be sentenced.

"I think all of this is much ado about nothing and frankly I look forward to being able to try this at some point," Brown's lead lawyer Mark Geragos said outside the court.

Evidence of Brown's conduct in Washington could lead him to face additional penalties in California because of his conviction for attacking pop singer and ex-girlfriend Rihanna in 2009. Brown was on probation in that case when he was arrested in Washington.

Los Angeles prosecutors and a judge had been awaiting the outcome of the Washington trial, but could consider additional punishments based on evidence and evidence presented during a probation violation hearing.

Los Angeles Superior Court judge Victor Greenberg refused to consider rulings in the Washington case during a brief hearing yesterday. Another of Brown's lawyers, Bob Kalunian, argued the singer should be released on his own recognisance or on bail.

The judge set a hearing for May 1 to determine when a probation violation hearing should be held. The hearing would cover evidence and evidence likely to be presented against the singer in Washington.

Mr Kalunian said the singer wanted the hearing as soon as possible and Judge Greenberg said it would probably happen before the Washington assault trial.

Brown entered anger management rehab in California shortly after his Washington arrest, but was dismissed from the Malibu centre in mid-March for breaking its rules. He was then jailed without bail and has been in custody since.

He was transported to the Washington area by the US Marshals Service and will now be sent back to California.