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.

"Although it's taken a long time, probably longer than it should have, what's happening here today is something our entire Army can celebrate and take pride in," Casey said.

Dunwoody comes from a long history of Army families. Dunwoody generations have fought in every US war since the War of Independence, Casey said.

"Today, we're lucky to live in extraordinary times, times that propel us closer to the ideals we stand for, live by, and defend," Casey said.

Dunwoody will head the Army Materiel Command, one of the Pentagon's largest outfits which is responsible for worldwide logistical and supply operations.

"I wish I could begin to describe the incredible feelings of gratitude, humility, and love that are absolutely consuming me at this very moment," Dunwoody said. "But it's impossible."