As his ex-girlfriend Rihanna was preparing to testify against him in a US court yesterday, the American R&B singer Chris Brown pleaded guilty to assaulting the pop star in February.

Brown entered his plea to one count of assault before a preliminary hearing – which was attended by Rihanna – was set to begin in Los Angeles.

The 20-year-old spoke softly throughout the hearing as he waived his rights and told the Superior Court Judge, Patricia Schnegg, that he understood the gravity of his plea.

“I think it's commendable you took responsibility for your conduct,” Judge Schnegg told the singer.

Brown will be sentenced in August, but the terms of the plea deal call for him to serve five years of formal probation and six months — roughly 1,400 hours — of community labour. Brown will be able to complete his probation in his home state of Virginia; he will have to do either graffiti removal or roadside clean-up for his service.

He will also complete a year of domestic violence classes, and pay fines. In exchange, he pleaded guilty to felony assault by means likely to cause great bodily injury. If he violates his probation, Brown faces four years in jail.

Brown was arrested on February 8, hours after police say he hit and threatened Rihanna after leaving a pre-Grammy party in Los Angeles where both were nominated for music awards. He was later charged with felony assault likely to produce great bodily harm and making criminal threats.

After Brown’s arrest, it was alleged that Rihanna, 21, had suffered a split lip, bloody nose and scratching to her face during the row. She was taken to hospital with contusions and facial swelling, according to reports at the time.

Judge Schnegg yesterday issued a stay-away order which means that Brown must remain at least 50 yards from Rihanna at all times, except at industry functions, where the distance is reduced to 10 yards.

The judge told Rihanna, who was wearing a demure black dress and pearls, that the order was not one way, and that she would have to stay away from Brown as well.

The case of the two celebrities caused headlines around the world and outside court yesterday paparazzi and mainstream media crews jostled for a shot of the two stars as they left court.

Rihanna, originally from Barbados, scored a worldwide hit with her chart-topping single Umbrella, while Brown rose to fame with his single Run It!. The pair dated for many months and toured together internationally before the assault incident.

After the hearing neither singer was available for comment, but Rihanna's lawyer, Donald Etra, said that she was satisfied by the outcome. "Rihanna believes that this is a fair and just resolution to this case," Mr Etra told reporters. "She's feeling fine. She understood what was happening in court. She did not object to the plea by Chris."

He said that Rihanna had been willing to testify against Brown, had the case gone to trial.

"She was fully prepared to testify to what happened that evening and she would have told the truth," Mr Etra said, brushing off questions concerning the state of Rihanna's current relations with Brown.

"It's inappropriate to discuss the terms of their relationship," he said. "Suffice it to say that there's a stay-away order."

Brown’s attorney, Mark Geragos, said that the singer was “very thankful to all the people who've been very supportive".

"This is a kid who's never been in trouble before, who wants to move past this and make sure that the message gets out that these kinds of things, of domestic violence, are not acceptable,” Mr Geragos said. “And that he has accepted responsibility and continues to do so and embraces this as an opportunity for him to get his life back on track and his career back on track."

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