WASHINGTON — As President Barack Obama considered adding as many as 40,000 U.S. forces to a backsliding war in Afghanistan in 2009, Vice President Joe Biden warned him that the military rationale for doing so was flawed, a new book about Obama's expansion of the conflict says.

The book, "Little America: The War Within the War for Afghanistan," also says that in planning the drawdown of troops two years later, the White House intentionally sidelined the CIA. Obama purposely did not read a grim CIA assessment of Afghanistan that found little measurable benefit from the 30,000 "surge" forces Obama eventually approved, the book quotes a U.S. official as saying.

A copy of the book by Washington Post correspondent Rajiv Chandrasekaran was obtained by The Associated Press. It will be released Tuesday.