Bush on Tuesday denied accusations that he had been negligent about the threat from Usama bin Ladin's group during his initial months in office.
Testifying before a commission probing the attacks on the US that killed 3000 people, Secretary of State Colin Powell and Defence Secretary Donald Rumsfeld also defended the administration.
"Had my administration had any information that the terrorists were going to attack New York City on September 11, we would have acted," Bush told White House reporters.
Rumsfeld told the inquiry there was no military means to prevent the hijacked aeroplanes from hitting the World Trade Centre towers in New York and the Pentagon in Washington.
"First, I know of no actionable intelligence since 20 January 2001 that would have allowed the US to attack and capture or kill Usama bin Ladin," Rumsfeld said.
"Had my administration had any information that the terrorists were going to attack New York City on September 11 we would have acted"
"Second, even if bin Ladin had been captured or killed in the weeks before 9/11, no one I know believes it would have prevented 9/11," he told the National Commission on Terrorist Attacks Upon the United States.
Rumsfeld said the 19 hijackers had been in the United States for months before the attack. Even if actionable intelligence had appeared, he said, "9/11 would likely still have happened".
Powell in his testimony said fighting terrorism" was a priority for the Bush administration from the time it took office.
The secretary of state said Bush decided early in his administration to aggressively fight terrorism.
"He said in early spring, I am tired of swatting flies. He wanted a thorough, comprehensive, diplomatic, military, intelligence, law enforcement and financial strategy to go after al-Qaida," Powell said.
"We wanted to move beyond the rollback policy of containment, criminal prosecution and limited retaliation for specific terrorist attacks. We wanted to destroy al-Qaida," Powell told the commission.
The commission, set up in 2002, has in an interim report blamed the Clinton and Bush administrations for failing to properly gauge the threat al-Qaida presented.
Its final report is expected by the end of July.