WASHINGTON, May 26 (Reuters) - The U.S. Supreme court on Tuesday issued a mixed ruling in a case involving whistleblower claims against KBR Inc in which the contractor was accused of defrauding the U.S. government over work it carried out in Iraq. On a 9-0 vote, the court sent the case back to an appeals court for further consideration. The ruling means that the case filed by former employee Benjamin Carter, who worked in Iraq as a water purification operator, is likely to continue. (Reporting by Lawrence Hurley; Editing by Will Dunham)