USA Swimming on Monday suspended Michael Phelps for six months, forced him to withdraw from next year's world championships and took away his funding from the sport's national governing body as a result of the Olympic champion's second DUI arrest.

USA Swimming said Phelps violated its Code of Conduct, and cited a section of its 2014 Rule Book in punishing Phelps, the winningest Olympian in history with 18 gold medals. Its executive committee approved the sanctions, which take effect immediately.

The suspension won't keep Phelps from training with his North Baltimore club, but the 29-year-old swimmer won't be allowed to participate in USA Swimming-sanctioned meets through April 6, 2015.

Phelps and USA Swimming also agreed that he won't compete in the world swimming championships in Russia next August. His monthly funding stipends will be stopped during the suspension.

Over the weekend, Phelps announced he was entering a six-week, in-patient program, a week after he was arrested and charged with drunken driving in his hometown of Baltimore.

"Michael's conduct was serious and required significant consequences," said Chuck Wielgus, USA Swimming executive director. "We endorse and are here to fully support his personal development actions."

This is Phelps' second time facing DUI charges. He was arrested and charged with drunken driving on Maryland's Eastern Shore as a 19-year-old in 2004, fresh from the Athens Olympics, where he won six gold medals.

Phelps pleaded guilty to the charges, but as a young first-time offender he avoided conviction. A judge imposed 18 months' probation and a fine but waived the conviction, which means Phelps faces the same penalties a first-time offender would.

If convicted of the latest charges, Phelps faces up to one year in jail, a $1,000 fine and the loss of his driver's license for six months.