Washington - A US Army officer on Friday became the first woman in American history to be promoted to the rank of a four-star general, the highest rank in the service.

General Ann Dunwoody received her fourth star in a ceremony at the Pentagon with Defence Secretary Robert Gates and Army Chief of Staff General George Casey.

The promotion marked the steady trend of shattering racial and sexual barriers in the United States, coming less than two weeks after Barack Obama became the first African American to win the White House.