 White phosphorous being used over Falluja |
General Peter Pace said that such munitions were a "legitimate tool of the military", used to illuminate targets and create smokescreens.
Two weeks ago, the US admitted using it to flush out insurgents in Falluja last year - raising concerns that it might have hit civilians.
Initially, the military denied using it against either insurgents or civilians.
Correspondents said having had to retract its original denial was a public relations disaster for the US.
'Within the law'
Gen Pace said no military went to greater lengths to avoid civilian casualties than the US army.
He said white phosphorus, a chemical that burns on exposure to oxygen, producing a bright light and lots of white smoke, was used primarily to illuminate a battlefield or to hide troop movements.
