Retired Gen. Wesley Clark, a key military adviser for Barack Obama, dismissed John McCain's war record as a qualification for readiness to be president.

Appearing Sunday on CBS' "Face the Nation," Clark downplayed the plane crash that led to McCain's captivity during the Vietnam War, and said the squadron McCain commanded "wasn't a wartime squadron."

"He has been a voice on the Senate Armed Services Committee. And he has traveled all over the world. But he hasn't held executive responsibility," Clark said.

When asked by host Bob Schieffer how he came to describe McCain as "untested and untried," Clark said it was "because in the matters of national security policy-making, it's a matter of understanding risk. It's a matter of gauging your opponents and it's a matter of being held accountable. John McCain's never done any of that in his official positions," adding, "He hasn't made the calls."

When Schieffer noted Obama has not had wartime experiences, Clark said: "Well, I don't think riding in a fighter plane and getting shot down is a qualification to be president."

McCain spokesman Brian Rogers issued a statement saying Obama's campaign is proving Obama does not stand "for a new type of politics."

McCain has not responded directly. He is scheduled Monday afternoon for a chat with reporters following a Harrisonburg, Pa., factory tour.

"The reality is he's proving to be a typical politician who is willing to say anything to get elected, including allowing his campaign surrogates to demean and attack John McCain's military service record," Rogers said.

"John McCain is proud of his record of always putting the country first -- from his time in the Navy, in Vietnam and through to today. And on the biggest question we've faced in recent years, the war in Iraq, the facts on the ground show that John McCain was right, as Barack Obama is about to find out after failing to visit there in over 900 days," he continued, and reiterated the standing offer to appear at joint town-hall meetings with McCain.

The exchange came a day after McCain questioned Obama's trustworthiness at a Louisville, Ky., fundraiser.

"You know, this election is about trust, and trusting peoples word, and unfortunately apparently on several items, Senator Obamas word cannot be trusted."

McCain had pointed to Obama's not voting on a resolution to condemn a MoveOn.org political ad; Obama's slowness to be briefed on Iraq; Obama's not taking him up on his offer to hold joint town hall meetings; and Obama's decision to forego the public campaign financing system.

The gist of Clark's comments were not new, but he had not said them in such a public forum.

In a March conference call with reporters while he was still backing Hillary Rodham Clinton, Clark said: "Everybody admires John McCain's service as a fighter pilot, his courage as a prisoner of war. There's no issue there. He's a great man and an honorable man. But having served as a fighter pilot -- and I know my experience as a company commander in Vietnam -- that doesn't prepare you to be commander in chief in terms of dealing with the national strategic issues that are involved. It may give you a feeling for what the troops are going through in the process, but it doesn't give you the experience first hand of the national strategic issues."

The Associated Press contributed to this report.