WASHINGTON – Was it his campaign’s slow response to the swift boat advertisements or the remark that he voted for Iraq war money before he voted against it that Senator Kerry regrets most from his failed bid for the White House?

Neither, according to Mr. Kerry’s reflection yesterday on what he considered his biggest mistake when trying to wrest the presidency from Presi dent Bush in 2004.

“I think the biggest mistake was probably not going outside the federal financing so we could have controlled our own message,” the Massachusetts senator said on NBC’s “Meet the Press.”

The Kerry campaign opted to accept federal money – and federal spending limits and other rules – after he won the Democratic nomination. The nominating convention in Boston occurred more than a month before the GOP renominated Mr. Bush, forcing Mr. Kerry to begin spending under federal rules much earlier than Mr. Bush.

“We had a 13-week general election, they had an eight-week general election. We had the same pot of money. We had to harbor our resources in a different way and we didn’t have the same freedom,” Mr. Kerry said.

“I think the most important thing would have been to spend more money, if we could have, on the advertising and responding to some of the attacks,”he said.

As for other missteps, Mr. Kerry said: “I made some mistakes. I know what they are, and I take responsibility for them.”

Some political observers believe the Kerry campaign should have acted more quickly in countering an anti-Kerry group, Swift Boat Veterans for Truth, that attacked his Vietnam War record.

The Bush campaign criticized Mr. Kerry relentlessly for his remark about voting for and then against an $87 billion bill for the military and reconstruction in Iraq and Afghanistan. The GOP used Mr. Kerry’s own words to support the contention that he flip-flopped on issues.

As for a run in 2008, Mr. Kerry said yesterday he would make a decision by the end of the year.