Jerome Corsi, author of Obama Nation, is escorted by immigration officers in Nairobi on Tuesday. (Associated Press)

The U.S. author of a book that attacks U.S. presidential candidate Barack Obama will be deported by Kenyan authorities before he can launch his book in the African country.

Jerome Corsi, who wrote The Obama Nation: Leftist Politics and the Cult of Personality, was detained by Kenyan officials on Tuesday in Nairobi.

Police said he was picked up at his hotel because he does not have a work permit for Kenya.

Kenyan immigration officials say he will be deported.

The book, which repeats rumours that the Democratic nominee was raised a Muslim, uses drugs and is consumed by "black rage," has been debunked publicly and on the website, FightTheSmears.com.

Corsi's book, which was to be launched Tuesday in Kenya, concludes that Obama is dangerous and radical.

Obama is, in fact, a Christian who attended Trinity United Church of Christ in Chicago and has no history of drug use or radicalism.

Obama's father, whom he barely knew, was a Kenyan economist and he is regarded as a native son there. Members of his extended family still live there.

He is wildly popular in Nairobi. Minibuses sport his picture and vendors sell T-shirts bearing his image.

An article in Kenya's oldest newspaper, The Standard, described Corsi's book as "a smear crusade."

Critics in the U.S. also say the book is meant to hurt Obama's poll prospects next month.