Democratic presidential candidate Wesley Clark (search) said Thursday it was up to Congress to determine whether President Bush's march to war in Iraq (search) amounted to a criminal offense.

Asked if it was criminal to mislead the nation in going to war, Clark told reporters, "I think that's a question Congress needs to ask. I think this Congress needs to investigate precisely" how the United States wound up in a war "that wasn't connected to the threat of Al Qaeda (search)."

The retired four-star general defended his recent comments against the war after both his Democratic rivals and top Republicans complained that the statements were inconsistent with past remarks by Clark, including testimony to Congress in October 2002.

Clark has called for a full congressional probe into why the United States went to war in Iraq, but his comments Thursday marked the first time he had hinted at possible criminal wrongdoing.

Asked by a reporter if he thought Bush might have committed an impeachable offense, Clark said, "Let's have that investigation done."

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Clark renewed his criticism that Bush misled the nation on Iraq. "This was an elective war," he said. "He forced us to go to war."

Clark denied that he had changed his position on the war, renewing his assertion that he had opposed it all along. Earlier in the day, Ed Gillespie, the RNC chairman, had traveled to Arkansas -- Clark's home state -- and criticized the Democratic candidates, singling out Clark and arguing that he had changed his position on the war for political gain.

The RNC also released a transcript of Clark's testimony in September 2002 to the House Armed Services Committee in which he called Iraqi leader Saddam Hussein a clear threat and said military action could not be postponed indefinitely.

Responding to criticism from Gillespie, Clark told reporters that it was a sign that his campaign was succeeding.

"It looks like they've finally figured out that I'm George Bush's greatest threat," he said, blaming it on White House political adviser Karl Rove.