Disgraced US sprinter Marion Jones [Images] was sentenced to six months in prison on Friday for lying to federal prosecutors about her steroid use, a stunning downfall for the five-time Olympic medallist.

US District Court Judge Kenneth Karas imposed the sentence after Jones, 32, pleaded guilty to two charges last October, when she retired from athletics and tearfully confessed to betraying the trust of her fans after years of denying she used performance-enhancing drugs.

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"Your honour, I absolutely realize the gravity of these offences and I am deeply sorry," Jones told the judge, crying as she begged not to be separated from her two young sons.

"I pray that you be as merciful as a human being can be."

Karas gave Jones six months for lying about steroid use and two months -- to run concurrently -- for misleading federal investigators about a check fraud case involving her ex-boyfriend, former 100-metres world record holder Tim Montgomery.

After hearing her punishment, Jones sobbed into the shoulder of her husband, Olympic sprinter Obadele Thompson. She has until March to turn herself over to authorities.

"I truly hope that people will learn from my mistakes," she said later in a brief statement to reporters.

Jones has been stripped of the five athletics medals she won in the Sydney Olympics [Images], three of them gold. All her performances as of September 2000 have been erased from the record books.

She confessed to lying to investigators in 2003 when she denied knowing that she swallowed the banned substance tetrahydrogestrinone (THG), known as "the clear," before the 2000 Olympics.

WRONG MESSAGE

Karas noted the elevated status of athletes in society and said using drugs sent the wrong message. He said he did not believe Jones' statement in October when she said she did not realize she was taking steroids until after the 2000 Games.

Jones had told the judge she believed she was ingesting flaxseed oil until July 2001, and suspected it had been a performance enhancer only when she was unable to train as intensively and did not recover as quickly after she stopped taking the substance.

"That is very difficult to believe, that a top-notch athlete, knowing that a razor-thin margin makes the difference, would not be keenly aware of what he or she put in her body," Karas said. "It was a troubling statement."

Jones, whose image from a triumphant Sydney Games was enhanced by a winning smile and joyous celebrations, now has become the biggest name in world sport to admit using steroids.

"Today's sentencing concludes a sad series of events," USA Track & Field Federation said in a statement. "It is a vivid morality play that graphically illustrates the wages of cheating in any facet of life, on or off the track."

Prosecutors had agreed to a light sentence because Jones was prepared to cooperate in a separate fraud investigation of her former coach and one-time Olympic relay gold medallist, Steve Riddick.

Riddick was convicted in May 2007 of bank fraud, bank fraud conspiracy and money laundering conspiracy. On Friday Karas sentenced him to five years and three months in prison.

Montgomery, Jones' ex-boyfriend, has pleaded guilty to bank fraud. A sentencing date has not yet been set.

Defence lawyers asked for mercy saying Jones had suffered public humiliation.

Jones once pulled in millions of dollars in product endorsements but is now in financial ruin.

The case comes amid other steroid scandals in US sport, including a special report by former US Sen. George Mitchell last month that named nearly 90 baseball players as suspected steroid users.

Major League Baseball home-run king Barry Bonds is under indictment for a similar offence, accused of lying to federal investigators about his steroid use. He has pleaded innocent and denies he ever used performance-enhancing drugs.

Like Bonds, Jones was ensnared in a federal probe into California's now-defunct BALCO lab that disgraced elite athletes in several sports.