Bush acknowledged on Wednesday that the current steep spike in violence in Iraq "could be" compared to the Tet Offensive, which is widely considered to be a key point in the souring of the US public on the Vietnam War.
Bush "was making a point that he's made before, which is that terrorists try to exploit pictures and try to use the media as conduits for influencing public opinion in the United States," said White House spokesman Tony Snow.
"We do not think that there's been a flip point," he said. "The president's determined it's not going to happen with Iraq, because you have a president who is determined to win."
The ongoing flare-up in violence in Iraq comes in the middle of a bitterly fought political campaign ahead of November 7 elections to decide control of the US Congress, with opposition Democrats largely pinning their hopes of victory on the unpopular Iraq war and Bush's poor poll numbers.
"It is possible -- although we don't have a clear pathway into the minds of terrorists, it is possible they are trying to use violence right now as a way of influencing the elections," said Snow.
"But the one thing that nobody should have any doubt about is that we're going win," said the spokesman.
Even the mention by Bush of the Vietnam War has loud political resonance. The war divided Americans at the time and remains a deeply sensitive subject four decades later.
The 1968 Tet Offensive launched by the Vietcong and the North Vietnamese against South Vietnamese and US forces was considered a military defeat but a psychological victory, in that it crystallised US public opinion against the war.
Bush raised the parallel on Wednesday for the first time when asked in an ABC News television interview about a comparison by Thomas Friedman, a New York Times columnist, of the strife in Iraq with the Tet Offensive.
"He could be right," Bush said. "There's certainly a stepped-up level of violence."
Bush said insurgents were trying "to inflict enough damage that we'd leave."
The upsurge in violence in Iraq comes ahead of US legislative and gubernatorial elections on November 7. The Tet Offensive occurred before US presidential elections, bolstering the anti-war camp and leading the Democratic president, Lyndon Johnson, to announce he would not seek re-election.
Bush's remarks appeared to put his Republicans on a slippery slope.
Although Defence Secretary Donald Rumsfeld made a similar analogy in June 2004, the Bush administration has always shied from the comparison.
The parade of bodies brought home from Vietnam seen on US television screens had more or less ended with the US retreat in 1973. Nearly 60,000 Americans were killed in Vietnam.
Since the US-led invasion of Iraq in March 2003, 2,772 US troops have been killed, according to a Pentagon tally. October already has proved to be one of the most deadly months for US forces.
Opposition Democrats have made Bush's handling of Iraq a major campaign issue, and public sentiment against the war is growing.
In the latest poll, published on Thursday, approval of the Republican-led Congress has sunk to its lowest point since the party took control from Democrats 12 years ago.
The NBCWall Street Journal poll found that only 16 percent of registered voters approved of Congress's performance, compared with 20 percent in early September, the lowest point since the 1994 elections that gave Republicans control of the Senate and House of Representatives.

Copyright AFP (Agence France-Presse), 2006