WASHINGTON (Reuters) -- The Pentagon said it was "very nervous" about ethnic tensions in Iraq between Arabs and Kurds despite initial talks between their leaders, and a top U.S. commander warned the feud over land and oil could still turn violent.
While the sectarian fighting that nearly ripped Iraq apart has died down, the row between northern Iraq's largely autonomous Kurdistan region and its Shi'ite Arab-led government in Baghdad is seen by Washington as one of the greatest threats to the country's fragile stability.
Al-Qaeda insurgents in Iraq's north have sought to exploit the tensions to remain strong even as their influence has waned elsewhere in Iraq, U.S. defense officials said, pointing to a string of more deadly bombings as evidence that the group was capable of reconstituting its "combat power."
Geoff Morrell, the Pentagon press secretary, said Washington was "heartened" last week when Iraqi Prime Minister Nuri al-Maliki met the Kurdish region's president, Masud Barzani, after more than a year of deadlock.
"But we are very nervous, continue to be, about the overall Arab-Kurd tensions," Morrell told a news conference.
U.S. troops, preparing to withdraw from Iraq by 2012, have intervened many times to defuse the row, and Washington has pushed for a settlement before its forces go home.
There have been tense standoffs between Kurdish troops and Iraqi forces. At the heart of the problem is the fate of Kirkuk, which produces a fifth of Iraq's oil, and other disputed areas that are home to a mix of Arabs, Kurds, and smaller groups.
"We are going to remain vigilant," Morrell said. "A certain number of U.S. forces are required in that country...in no small measure to try to assist...the Arabs and the Kurds solve some of these problems while we are still there."
Describing Arab-Kurdish tensions as one of the "most dangerous" threats to Iraq's stability, Major General Robert Caslen, the commander of U.S. forces in the country's north, said the situation could "certainly resolve in an ethnic, lethal force engagement between Kurds and Arabs."
Briefing reporters in Washington via satellite from Iraq, Caslen said efforts were under way to keep a lid on sectarian tensions following the bombings near Mosul, the capital of the northern province of Nineveh.
Since June 30, when U.S. troops in Iraq withdrew from urban centers, the average number of attacks per week in Mosul has dropped to 29 from 42 before the pullback, Caslen said.
"What has increased, however, is the capability [of Al-Qaeda] to conduct the high-profile attacks," he said. "So you see an increase in the numbers of casualties post-30 June."
He said it was unclear whether Iraqi security forces would be capable of reining in Al-Qaeda in Mosul, where the Pentagon believes the group's leadership is concentrated.
Bombs killed 42 people across Iraq on August 10, ripping through mostly Shi'ite areas and raising fears of a resurgence in sectarian violence. Last week, a string of bombings targeting Shi'ites killed 44 people. Sunni Islamist militants such as Al-Qaeda, who consider Shi'ites heretics, are often blamed.
The recent attacks, Caslen said, showed that Al-Qaeda insurgents "still have the capability and they remain, I would say, a resilient force that has a capability to regenerate their combat power if necessary."
"They recognize how important it is to have these high-profile attacks in order to...entice the sectarian violence," Caslen said. "We have not found the sectarian reactions which, I think, is good."