CHICAGO - MICHELLE Obama has resigned from her job as vice-president of the University of Chicago medical centre to concentrate on being the country's first lady, her former boss said on Monday.

'Michelle Obama has resigned her leadership post at the University of Chicago Medical Centre as she prepares to take on her new role at the White House as First Lady,' the centre said in a statement.

'We are so very proud of Michelle personally, and we are very thankful for her professional accomplishments in creating and expanding the strategic vision for the Office of Community Affairs,' said James Madara, the centre's director.

Mrs Obama who will become first lady when her husband, Barack Obama, is sworn in as president on Jan 20, was the centre's vice-president for community and external affairs.

In 2007 she went part-time and then finally took unpaid took leave in order to help her husband during his White House campaign.

The Obamas arrived in Washington at the beginning of January to allow their two daughters, Malia and Sasha, to start their new school at the beginning of term.

Michelle Obama, who is a trained lawyer, will celebrate her 45th birthday on Jan 17, just three days before the inauguration. -- AFP