Madonna is critical of the current US government

The singer describes the retired US general as "a perfect example of the American Dream" and "a national hero".

"I'm supporting Wes Clark because in him I see the qualifications, character and vision we so desperately need," she said. "He is smart and he is good."

Madonna plans to hold a fundraiser for the former Nato commander at her Los Angeles home later this year.

In her letter, Madonna said she had never previously aligned herself with a presidential candidate during the primary campaign stage.

'American citizen'

She added that people "seem to pay attention to everything I do. So I am hoping they pay attention to this".

Madonna said she was backing Mr Clark "not only as a 'celebrity' but as an American citizen and as a mother".

She added: "I want my children to grow up with the same opportunities that I had - to know and understand what's going on in the world and to travel that world safely and with pride."

Mounting a fierce criticism of the current Bush administration, she said: "Our greatest risk is a lack of leadership, a lack of honesty and a complete lack of consciousness."

Madonna, who lives mostly in London, first publicly supported Mr Clark on US TV network CNN in December, describing him as a "natural born leader".