WASHINGTON - White House political adviser Karl Rove raised questions in early 2005 about replacing some federal prosecutors but allowing others to stay, an email released Thursday shows.

The one-page document, which spans emails between the White House and the Justice Department in January 2005, also indicates Attorney General Alberto Gonzales was considering a range of options in dismissing U.S. attorneys early in President Bush's second term.

But it concludes with Gonzales' top aide warning that an across-the-board housecleaning "would certainly send ripples through the U.S. attorney community if we told folks they got one term only."

The emails released Thursday by the Justice Department indicated that Gonzales and his then-chief aide, Kyle Sampson, suggested replacing 15 per cent to 20 per cent of federal prosecutors they identified as underperformers.

Sampson resigned under fire this week over the Justice Department's mishandling of the firings of eight U.S. attorneys -- and misleading Congress about the process.