WASHINGTON (AP) -- President Bush will tell the nation Wednesday night he will send more than 20,000 additional American forces to Iraq, acknowledging that it had been a mistake earlier not to have more American and Iraqi troops fighting the war, a senior administration official said.

Seeking support for a retooled strategy to win support for the unpopular war, the president also will acknowledge that the rules of engagement were flawed, White House counselor Dan Bartlett said.

For a little over 20 minutes Wednesday night, Bush is to explain why a gradual buildup of about 20,000 additional U.S. troops, along with other steps expected to include pumping $1 billion into Iraq's economy, is the answer for a more than 31/2-year-old war that has only gotten deadlier with no end in sight.

Bartlett did a round of interviews on television morning shows to set the stage for the president's address.

"A vast majority of the American people are not satisfied with the progress in Iraq," Bartlett said. "President Bush is in their camp. He's not satisfied, he's going to say the strategy was not working, he's going to tell them specifically how we're going to fix the strategy."