Brigadier General Steve Lanza, the spokesman for US forces here, added that "malign" influences from Iran and Syria are on the decline but remain a concern.

"We assess Arab-Kurd tensions as the number one driver of instability in Iraq," Lanza told reporters at a press conference in central Baghdad.

"We are working very hard to help reduce tensions in northern Iraq," he noted, adding that a committee made up of top US commanders, senior members of the Kurdish government in Arbil, and the central government in Baghdad are meeting to discuss confidence-building initiatives.

He noted that no such initiatives have yet been tabled, but General Ray Odierno, the top US commander in Iraq, said in August that the US was discussing arrangements that could see its troops work alongside Iraqi and Kurdish forces in disputed areas of northern Iraq.

Kurdish leaders have long demanded that their autonomous region comprising three provinces be expanded to include historically Kurdish-inhabited parts of Nineveh and Diyala as well as all of Kirkuk.

Baghdad, however, says the Kurdish region's borders should not extend past Arbil, Sulaimaniyah and Dohuk provinces.

Lanza said any initiatives will need the approval of Iraqi Prime Minister Nuri al-Maliki and Kurdish President Massud Barzani, must be in accordance with a Washington-Baghdad security agreement signed last year and should ensure that any involvement of US troops is temporary.

"We are going through every procedure possible right now to bring those two (Iraqi and Kurdish) armies together for the good of Iraq," he said.

On foreign interventions in Iraq, Lanza said that "the malign influence of some ... would indeed like to fracture this country and ... would not like the elections to occur in a credible and legitimate manner," referring to nationwide parliamentary elections due in January.

"It is no secret that foreign fighters have come into Iraq from Syria.

"There is influence from Iran, there is malign influence in this country, whether it be in money, whether it be in training, whether it be in resources or weapons systems that have come into this country."

He continued: "I would say in both those -- both foreign fighters coming in from Syria and malign influence not only from Iran but from other countries -- we have seen a downturn."