The bitter exchange marks an escalation in the political fight over Bush's plan, unveiled last week to a skeptical public, to send 21,500 more troops to Iraq as part of a new war strategy.
Bush, faced with opinion polls showing Americans strongly oppose a troop increase, is expected to defend his Iraq plan in his State of the Union speech on Tuesday.
Pelosi, who earlier this month became the first woman to lead the House, insisted on Friday that Democrats would never deny funding to US forces in wartime.
"Bush's strategy has failed totally in Iraq"
Dimos, Hania-Crete, Greece
Send us your views
She said: "... we will hold the president accountable.
"He has to answer for his war. He has dug a hole so deep he can't even see the light on this ... It's a historic blunder."Perino said: "Speaker Pelosi was arguing in essence that the president is putting young men and women in harm's way for tactical political reasons." She described Pelosi's comments as "poisonous".
Asked whether she was accusing Bush of manipulating the timing of the new deployment to avoid congressional action, Pelosi said: "I would certainly hope he didn't manipulate the timing of sending the troops in. I think he could have told us about it sooner."
Perino said Bush was "sending the troops to Iraq quickly because he wants to win".