By Deborah Charles

WASHINGTON (Reuters) - Democrats accused John McCain on Wednesday of being confused and unsympathetic for saying it's "not too important" when U.S. troops leave Iraq, attacking the Republican presidential candidate on an issue he has made key in the November election.

McCain's campaign said his comment had been distorted and there was no one better placed than the former prisoner of war to understand the sacrifices made by American soldiers and military families.

The Arizona senator has built his campaign largely around his strength as a potential commander in chief and has drawn contrasts with his Democratic rival Barack Obama who McCain says is too inexperienced in foreign policy.

But Democrats seized on McCain's response to a question in a television interview when asked if he had a good estimate of when he thought American troops might come home from Iraq.

"No, but that's not too important," McCain said on NBC's "Today Show." "What's important is the casualties in Iraq."

In dueling conference calls, the campaigns propelled Iraq and the squabble over national security credentials back to the front of the campaign agenda. The focus this week had been on the U.S. economy, an issue that many analysts believe favors Obama.

"It is unbelievably out of touch and inconsistent with the needs and concerns of Americans and particularly the families of the troops who are over there," said Democratic Sen. John Kerry of Massachusetts.

"To them it's the most important thing in the world when they come home. And it's the most important thing in the world that we have a commander-in-chief who understands how you can bring them home," said Kerry, a Vietnam veteran and close Obama supporter who lost the 2004 election to President George W. Bush.

McCain's campaign said the Democratic reaction was a false attack designed to hide Obama's willingness to disregard facts as he pursues withdrawal from Iraq "no matter what the costs."

Later the Obama campaign sought to quell controversy over the head of its vice presidential selection team whose business dealings had been questioned. Obama announced that Jim Johnson, former head of the mortgage giant Fannie Mae, had quit.

On Iraq, Republican National Committee Chairman Mike Duncan said Obama, an early opponent of the war who has promised to remove U.S. combat troops within 16 months of taking office, had no "credibility" discussing the future of the country.

Sen. Joe Lieberman, an independent from Connecticut, said he was disappointed in the "reflexive attacks" on McCain, a prominent supporter of the decision to invade Iraq who has vowed to keep American troops there until the war is won.

"I view the attacks on Senator McCain this morning as another partisan attempt to distort John McCain's words, to distract the American people from the fact that John McCain has been both courageous and right about the surge in Iraq and Barack Obama has unfortunately been consistently wrong," said Lieberman, a former Democrat who is a McCain supporter.

"The part that I find most outrageous is the suggestion that he's out of touch with the needs of our troops," he said.

Obama's advisers said McCain's comment shows that he is confused and does not really understand the situation in Iraq.

"We've heard ... a real disturbing, even disconcerting, pattern of confusing the basic facts and reality that pertain to Iraq from John McCain over a series of months," said Susan Rice, one of Obama's senior foreign policy advisers.

She pointed to misstatements McCain has made about the number of troops in Iraq and his confusion over which Islamic extremist group Iran is accused of supporting.

Democratic National Committee Chairman Howard Dean said the comments show McCain has no plan to bring the Iraq war to a responsible end.

"One of the most important questions in this campaign is when and how Sen. McCain would bring our troops home from Iraq," Dean said.

(Editing by David Wiessler)

(To read more about the U.S. political campaign, visit Reuters "Tales from the Trail: 2008" online at http://blogs.reuters.com/trail08/)