Top Pentagon advisers have warned that time is running out for the United States to establish law and order in Iraq, where another US soldier was killed by a bomb on Friday.
US troops are under pressure in Iraq, as are their leaders at home
The latest victim was the 34th US soldier to be killed since hostilities were officially declared over on 1 May.
The overall US death toll since the war began - 148 - is now higher than the total US fatalities in the 1991 Gulf War.
A senior advisory team sent to Iraq by the US Defence Department has called for urgent action in the next three months to provide security, basic services and political and economic opportunity for the Iraqi people.
The team says that, without rapid change, there is a growing potential for real chaos.
In the latest attack, a bomb exploded in the flashpoint western town of Falluja, 50 kilometres (32 miles) west of Baghdad, killing one US soldier.
A US military spokeswoman said the
soldier's Humvee - part of a 3rd Infantry division convoy - drove over the device on the main Falluja bridge over the Euphrates River.
Earlier, a witness reported seeing four US soldiers evacuated from the scene and said three US Humvee vehicles were badly damaged, the Associated Press reported.
Falluja is in the "Sunni Triangle" - an area north and west of Baghdad where supporters of ousted President Saddam Hussein are active and where US forces have been repeatedly attacked.
US forces on Friday blew up a bronze statue of the former leader posing on horseback near the gate to his former palace compound in Tikrit, his home town.
Allies defend war
The BBC's Jonny Dymond, in Baghdad, says that on average there are 13 attacks on coalition forces every day.
UK Prime Minister Tony Blair and US President George W Bush again defended the war against Iraq after Mr Blair made a speech to a joint session of Congress on Thursday.
President Bush vowed to "finish the task" of putting Iraq on course for democracy.
"We are being tested in Iraq," said the president. "Our enemies are looking for signs of hesitation. They are looking for weakness. They will find none."
Mr Blair said that, even if they had been wrong about weapons of mass destruction, history would forgive the removal of Saddam Hussein.
The Pentagon report - assessing post-war reconstruction efforts in Iraq - was issued as US Deputy Secretary of Defence Paul Wolfowitz began an extensive five-day tour of the country.
Mr Wolfowitz said his purpose was to thank US troops and to see for himself what it was, in his words, "for the Iraqi people to be liberated".
The Pentagon advisory team was led by John Hamre, financial controller of the defence department during the Clinton era, and current head of the respected Center for Strategic and International Studies.
Dr Hamre and his colleagues urge the Bush administration to immediately "turbo-charge" reconstruction efforts, by swiftly injecting funding and personnel and securing the involvement of other countries and the United Nations.
"The next three months are crucial to
turning around the security situation, which is volatile in key parts of the country," the report says, adding that the US must also be ready "to stay the course in Iraq for several years".
The team says more Iraqis should be employed in the rebuilding - and communication with Iraqis had to be improved. It says the new Iraqi Governing Council has a vital role.