A Singapore businessman has pleaded guilty to defrauding the United States as part of a widening bribery scandal involving contracting services for US Navy ships. Alex Wisidagama, 38, a citizen of Singapore and cousin of the executive running the firm at the center of the corruption scandal, admitted to submitting fake invoices to overcharge the US Navy for fuel, port tariffs and other services at inflated prices, authorities said. He entered his plea in an agreement with prosecutors in federal court in San Diego, California. Wisidagama is the second person to plead guilty in the case that has rocked the American navy and ensnared several officers, fueling concerns about a possible ethics crisis in the military's senior ranks. In December, former Naval Criminal Investigative Service special agent John Beliveau pleaded guilty to conspiracy to commit bribery after admitting to providing the ship supply company Glenn Defense Marine Asia with sensitive information in return for cash, hotel rooms and prostitutes. Wisidagama is due to be sentenced on June 13. His cousin, Leonard Francis, is the key figure in the case as he owns the ship supply firm GDMA. According to prosecutors, officers dubbed Francis "Fat Leonard" for his girth and his penchant for allegedly showering favors on sailors in return for preferential treatment for his firm. The US Navy paid hundreds of millions dollars in husbanding services to GDMA, including fees for providing tugboats, fuel, water and removing garbage. Two US Navy commanders have been charged in the bribery case.