US Defense Secretary Robert Gates is concerned about possible misconduct in Afghanistan by the private security firm formerly known as Blackwater and has promised to review the issue, the Pentagon said.

Gates made the pledge to lawmakers after receiving a letter from Carl Levin, the chairman of the Senate Armed Services Committee, who urged the defense secretary to reconsider awarding a possible one billion dollar (RM3.34 billion) contract to the firm, now known as Xe, due to allegations of wrongdoing.