Sources said White House lawyers have told President Bush he would not need congressional approval to launch an attack against Iraq.
Two senior administration officials said White House counsel Al Gonzales advised Bush earlier this month that the Constitution gives the president authority to wage war without explicit authority from Congress.
White House spokesman Ari Fleischer declined to confirm that Bush had received an opinion from Gonzales on the matter.
"Any decision the president may make on a hypothetical congressional vote will be guided by more than one factor," Fleischer said.
Despite the go-ahead from his legal advisers, the officials said the president has not ruled out seeking lawmakers' approval if he decides to attack Iraq.
The officials noted that Bush's father was told in advance of the 1991 war that he did not need congressional authority to act, but nonetheless sought Congress' blessing for his action.