A 29-year-old man pleaded guilty Tuesday to recruiting and prostituting a 15-year-old girl, admitting in federal court that he and his girlfriend arranged for the teen to perform various sex acts for money across the D.C. area.

In a brief hearing in federal court for the Eastern District of Virginia, Ronnie P. Holmes told a judge that the girl claimed to be 18, but he admitted that he had enough information to know better. He pleaded guilty to a charge of sex trafficking of a child — an offense which carries with it a mandatory minimum penalty of 10 years in prison and a possible life term.

Fairfax County police initially arrested Holmes and his girlfriend, Stephanie Chapman, 27, at an Alexandria hotel in March after the 15-year-old called her mother to say she “was being prostituted and needed help,” court filings show. Investigators later found that Holmes, who went by the nickname “King,” had been prostituting the girl since late February, giving her the nickname “Diamond” and advertising her services on the Web site www.backpage.com, court filings show. He met the girl outside a Lorton apartment, where at the time he was sleeping in a car, the filings show.

Chapman was also charged with sex trafficking of a child and her case is ongoing, authorities said. Holmes is scheduled to be sentenced at 9 a.m. on Sept. 27.