WASHINGTON (AP) - The top U.S. commander in Iraq told a Senate panel Thursday that improving security in Baghdad would take fewer than half as many extra troops as President Bush has chosen to commit.

Testifying before the Senate Armed Services Committee on his nomination to be Army chief of staff, Gen. George Casey said he had asked for two additional Army brigades, based on recommendations of his subordinate commanders. Bush announced Jan. 10 that he would send five extra brigades as part of a buildup that would total 21,500 soldiers and Marines.

Asked by Sen. John Warner, R-Va., why he had not requested the full five extra brigades that Bush is sending, Casey said,