In the northern city of Mosul on Wednesday, a van tried to swerve inside a joint convoy of US and Iraqi military vehicles, but exploded prematurely, killing an unknown number of civilians, US army Sergeant Chris Schaeffer said.
A second car parked on a street nearby exploded and killed two Iraqi soldiers, Schaeffer said.
The northern metropolis of 1.5 million people has become a battle terrain for fighters and US forces, with the 30 January polls seen as a referendum on who truly controls the city.
Meanwhile, the group Ansar al-Sunna, in an internet statement, has claimed responsibility for an attack in Baghdad in which four bank guards were burnt to death in a van carrying new bank coins.
Also in the capital, a policeman was shot dead and an official in the town of Baquba was gunned down, police and witnesses said.
In Duluiya, Iraqi soldiers opened fire on a car that did not stop at a checkpoint, killing three civilians, police said, while four Iraqi soldiers were killed in attacks around Samarra.
US troops in the capital snatched six men they said were linked to last week's assassination of Baghdad Governor Ali al-Hadairi, the US army said.
A US marine assigned to 1 Marine Expeditionary Force was killed in action on Tuesday in Anbar province, the US military said on Wednesday.
US forces have stepped up raids
in the strife-torn city of Mosul
The unrelenting dose of daily car bombs and assassinations has forced a hard reality check on the White House and US-backed interim government.
Asked if he agreed with interim Iraqi Prime Minister Iyad Allawi that violence will make voting impossible in some areas of the war-torn country, White House spokesman Scott McClellan said: "We all recognise that the election is not going to be perfect."
For his part, Foreign Minister Hushiar Zibari told an Egyptian newspaper the election would go ahead as planned on 30 January but conceded there would be problems in ensuring a nationwide vote.
"The elections will not be perfect, nor organised 100%. There will be problems but we will hold them because the majority of people want them," Zibari said.
The second in command of US forces in Iraq, Lieutenant-General Thomas Metz, also conceded last week the situation remained volatile in the Anbar, Nineveh, Salahuddin and Diyala provinces.
As the clock ticked down to polling day, fears of internal Iraqi political strife mounted as a small Sunni Muslim party, the National Front for the Union of Iraq, said it was quitting the electoral race on Wednesday due to the arrest by US troops of its leader, Shaikh Hasan Zaidan Khalaf al-Lahibi on 31 December.
On the other hand, a top Shia party vowed to cleanse the security forces of ex-Baathists and Allawi's Iraqi National Accord party cried foul over the alleged use of religion by Shia political candidates.
Iraqi policemen have borne the
brunt of the ongoing violence
Allawi's party lodged a formal complaint against the joint Shia list, the Unified Iraqi Alliance, for violating state law by allegedly using religion in its advertising.
US Secretary of State Colin Powell added his voice to a growing debate when he said on Wednesday that US troops could start withdrawing from Iraq this year as Iraqi forces take over security in the country.
In an interview with National Public Radio, Powell was unable to say how quickly US forces might be able to pull out of the country or what their troop levels in Iraq would be at the end of 2005.
"But with the money we're putting into the growth of the new Iraqi army and National Guard and police force, I believe that during 2005 they will be able to assume a greater burden," the outgoing chief US diplomat said.
Bremer hits back
Also on Wednesday, Paul Bremer, the former US administrator in Iraq, wrote in a newspaper column that disbanding the Iraqi army after US-led forces took control of the country had been the right decision.
Writing in the Wall Street Journal, Bremer compared Iraq's military and Baathist Party leadership under former president Saddam Hussein to the Nazi regime of German dictator Adolf Hitler.
After Saddam's overthrow in April 2003, "it was vital to reassure the Iraqi people that in the new Iraq these organisations would no longer be used as instruments of repression", Bremer said.
Bremer has vigorously defended
the move to disband Iraqi army
Bremer was the head of the US-led Coalition Provisional Authority in Iraq from May 2003 to June 2004.
Citing opinion polls taken in 2003, Bremer argued that the Iraqi population strongly supported the move to fully dismantle the Saddam dispensation.
Moreover, he said, there was no Iraqi army to keep in place by mid-April 2003. "By the time Baghdad and Tikrit fell, the Iraqi army had already disbanded itself," he wrote.
Bremer said the decision was approved by the US military and civilian leadership, and added that most of the newly constituted Iraqi army are soldiers from the old one.