George Bush appears to have first used the controversial term in an interview with CNN television, when he noted the violence in Iraq and said that the December 2005 elections "seems like a decade ago".
Tony Snow, the White House spokesman, said: He is not talking about the war as a comma.
"What the president's making the point is, when you look at a history book, the ten-month period is a comma," he said. "What he means is that, in the grand sweep of history, 10 months is not an epic."
Bush told CNN in the late September interview: "I like to tell people when the final history is written on Iraq, it will look like just a comma because there is - my point is, there's a strong will for democracy."
He used the same image on Tuesday at a political fundraiser in California, telling Republican party faithful: "It must seem like an eternity to you, when you think about those elections last December."
"What the president's making the point is, when you look at a history book, the ten-month period is a comma"
Tony Snow, the White House spokesman
"It certainly does to me, in some ways. Ultimately, when this chapter of history will be written, however, it's going to be a comma."
"The Iraqis voted, comma, and the United States of America understood that Iraq was a central front in the war on terror and helped this young democracy flourish so that a generation of Americans wouldn't have to worry about the extremists emanating from that country to hurt the American people," he said.
Snow fired back at unnamed critics he accused of trying to "wrench a statement out of context" to use it as ammunition against Bush "who is deeply aware of the human costs of war."
"Some people have tried to say, 'How dare the president refer to this as a comma? He's being glib about the deaths of Americans.' That's outrageous. And the people who say that know it," said the spokesman.