General John Abizaid, head of US Central Command, had initially stated that the security gap could be filled by Iraqi security forces and more international troops deployed to protect the UN-organised elections.
But his remarks after closed-door sessions with congressional armed services committee members late on Wednesday in Washington raised the prospect that the US may have to enlarge the 140,000-strong force deployed in Iraq, at least during the elections.
"I think we will need more troops than we currently have to secure the election process in Iraq that will probably take place in the end of January," Abizaid told reporters.
The statement is in contrast to recent calls to "bring our troops home", and may signal a new chapter in the Iraq debate between Democrats and Republicans.
The issue of whether the US has committed sufficient forces in Iraq to impose order is a touchy one for President George Bush, who has come under fire from Democratic challenger Senator John Kerry for Iraq's slide into bloodshed.
"But it is our belief that those troops will be Iraqi troops. And they may be additional international troops that arrive to help out as well, as part of the United Nations mission," he said.
"And so I don't foresee a need for more American troops, but we can't discount it."
Critics have charged that the US force is too small to pacify Iraq, while US Defence Secretary Donald Rumsfeld has repeatedly insisted that Abizaid has been given and will be given all the forces he asks for to get the job done.
Abizaid: Securing Iraq elections
may need additional US troops
Rumsfeld, who was with Abizaid on Wednesday, bristled when reminded that former army chief of staff General Eric Shinseki warned Congress before the US invaded Iraq in March 2003 that several hundred thousand troops would be needed to occupy the country.
He said General Tommy Franks, who led the invasion of Iraq and was Abizaid's predecessor at the Central Command, had asked for a smaller force of about 200,000, including troops in Kuwait.
"And the numbers that were provided were the numbers that were asked for by the combatant commander," Rumsfeld said.
"There is no mystery about it. Nobody turned him down. Nobody said it should be a smaller number. And the people who are running around the world saying that simply are wrong."
End of deployment
Separately, New Zealand Defence Minister Mark Burton said in a statement on Thursday his country's military personnel in Iraq will be home on Saturday.
New Zealand PM Helen Clark (R)
thinks Iraq is 'just too difficult'
The 61 army engineers, who have been based in Basra in southern Iraq, were due to leave by the end of the month after a year-long deployment.
They are to be flown out on a military Boeing 757 and be greeted by Prime Minister Helen Clark at Ohakea base, north of here.
Clark earlier said it was unlikely any further deployments would be made. "I can't see that at this time. I think Iraq is just too difficult and too dangerous," she told Radio New Zealand on Wednesday.