WASHINGTON — President Bush conceded yesterday that the specter of American failure in Vietnam is haunting the country’s campaign in Iraq.

In a television interview, Mr. Bush was asked if the current level of violence in Iraq represented a turning point comparable with the 1968 Tet offensive, which destroyed popular support for the Vietnam War.

The New York Times columnist Thomas Friedman wrote on Wednesday that insurgents in Iraq appear to have embarked on a frenzy of violence in the run-up to November’s elections in America. Their strategy, he suggested, was to force a drawback of American troops.

“He could be right,” Mr. Bush said. “There’s certainly a stepped-up level of violence, and we’re heading into an election.”

Tony Snow, the White House spokesman, said while Mr. Bush had acknowledged the comparison with Vietnam had merits; his resolve to prevail over the insurgency in Iraq was undiminished. The Tet offensive forced President Lyndon Johnston to withdraw from politics but the war in Vietnam dragged on for seven years. “The president’s determined it’s not going to happen with Iraq, because you have a president who is determined to win,” Mr. Snow said.

Parallels with Vietnam have bedeviled the American campaign in Iraq since the run-up to war. Six months before the invasion, Tariq Aziz, the former Iraqi deputy prime minister, said the regime would model its resistance on the Vietcong guerrillas.

“People say to me, ‘You are not the Vietnamese. You have no jungles and swamps’,” he said. “I reply, ‘Let our cities be our swamps and our buildings our jungles’.” Mr. Bush said yesterday that belief was still driving America’s opponents in Iraq. “My gut tells me that they have been trying to inflict enough damage that we’d leave,” he said.

“The leaders of Al Qaeda have made that very clear. They are trying to not only kill American troops, but they’re trying to foment sectarian violence. They believe that if they can create enough chaos, the American people will grow sick and tired of the Iraqi effort and will cause government to withdraw.”

With a report from a panel of elder statesmen, the Iraq Study Group, coming to define Washington’s debate over Iraq, the White House has been forced to rule out a series of withdrawal options.

Mr. Bush gave warning that American troops would remain in Iraq for the duration of his presidency. He said: “You mean every single troop out? No.” Mr. Snow was also forced to reject a suggestion that the White House would accept division of Iraq into three ethnic statelets on the ISG’s recommendation. He said: “Partitioned — nonstarter.”

Major General William Caldwell, a spokesman for American troops in Iraq, admitted that recent violence had a “disheartening” impact on the coalition.

An initiative to stabilize security in Baghdad had not met targets. He said: “‘Operation Together Forward’ has made a difference in the focus areas but has not met our overall expectations in sustaining a reduction in the level of violence.”