Intelligence reports that Iraq had weapons of mass destruction was a major rationale for going to war.
The U.S. senator from Massachusetts said the congressional resolution gave Bush "the right authority for the president to have."
But he told reporters on a campaign swing through Arizona, "I would have done this very differently from the way President Bush has." He challenged Bush to answer four questions.
"My question to President Bush is why did he rush to war without a plan to win the peace?" Kerry asked. "Why did he rush to war on faulty intelligence and not do the hard work necessary to give America the truth?
"Why did he mislead America about how he would go to war? Why has he not brought other countries to the table in order to support American troops in the way that we deserve it and relieve a pressure from the American people?
"There are four, not hypothetical questions like the president's, but real questions that matter to Americans," Kerry said. "And I hope you'll get the answers to those questions because the American people deserve them."
Bush's campaign has hammered Kerry over his vote to authorize military action and his vote a year later against $87 billion in funding for the ongoing wars in Iraq and Afghanistan.
Kerry has said he voted against that measure because it would have financed the war with borrowed money. He voted for a defeated alternative that would have rolled back some of Bush's tax cuts to pay for the conflict.
The president told supporters Monday in Virginia that he still would have gone to war based on the evidence at hand at the time, and he challenged Kerry to say whether he would have cast the same vote.
