The US military said on Thursday it was reviewing strategy in Baghdad, where US reinforcements have failed to halt spiralling violence, and expressed grave concern about mounting troop deaths.
The battle for control of Baghdad, which US officials say will decide Iraq's future, and a spate of attacks across Iraq on Thursday that killed at least 38 people piled pressure on US President George W. Bush before the November mid-term election.
In Washington, a senior administration official said the latest Baghdad security strategy had not achieved its goal and the top US commander in Iraq, Gen. George Casey, was expected to present a revised plan within weeks.
"Everybody understands you've got to have progress on the security issue in Baghdad," the official said.
The US military will be looking at the "adequacy" of Iraqi forces deployed in Baghdad, whether to change the balance of Iraqi police and soldiers in the city, and the role of US troops there, the official said.
Bush, whose Republicans are battling to retain control of the US Congress, said he saw a possible parallel in the rise in violence in Iraq and the 1968 communist Tet offensive, which triggered a drop in Americans' support for the Vietnam War.
Asked in an ABC interview whether he agreed the violence in Iraq was the "jihadist equivalent of the Tet offensive," Bush said: "(It) could be right. There's certainly a stepped up level of violence and we're heading into an election."
Bush said al Qaeda was very active in Iraq and trying to foment sectarian violence as well as kill US troops.
"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," he said.
Later at a Republican fund-raising event, Bush said: "There is one thing we will not do. We will not pull out our troops from Iraq before the terrorists are defeated."

.SECTARIAN MILITIAS
A spokesman said Casey had ordered the review of strategy in Baghdad, widely seen as crucial to bringing enough stability to Iraq to allow US troops to eventually leave the country.
US Maj. Gen. William Caldwell said the number of attacks targeting security forces in Baghdad had risen since US troops launched a crackdown designed to end sectarian violence killing dozens of people every day.
US commanders have blamed the rise in US casualties in Baghdad on more perilous patrolling by US forces trying to defeat sectarian militias and Sunni Arab insurgents opposed to the government.
Caldwell said violence across the country had risen by at least 20 percent in the first three weeks of the holy month of Ramadan, compared to the previous three weeks.
He said civilian casualty levels in Baghdad stabilised in October, but added: "Operation Together Forward has made a difference in the focus areas but it has not met our overall expectations of sustaining a reduction in ... violence.
"We are working very closely with the government of Iraq to determine how best to refocus our efforts," he said.
Lt. Col. Christopher Garver said Casey ordered the review last week. "US casualties are a grave concern but that is not driving the review," Garver told Reuters.
The US death toll rose on Thursday to 73 for October, which could become one of the deadliest months for US forces since a massive offensive in Falluja two years ago.
In Mosul, six suicide bombers including one in a fuel truck blew themselves up near police stations and US patrols, and insurgents fired mortar bombs and clashed with police in violence that killed at least 20 and wounded dozens.
A car bomb in Kirkuk killed at least eight people in an attack aimed at an Iraqi army patrol. In Khalis, a roadside bomb ripped through a busy market, killing 10 and wounding 20.
More than 2,780 US troops have been killed since the March 2003 invasion to topple Saddam Hussein.
Many more Iraqis have been killed and more than 300,000 have fled their homes in what some fear could lead to a sectarian partition of Iraq.
But the White House branded as a "non-starter" any suggestion of setting up semi-autonomous Shia, Sunni and Kurdish regions, as a top-level commission worked on recommendations for Bush on strategy over Iraq.