Enlarge By Hyungwon Kang, Reuters Gen. Ray Odierno, commander of the Multi-National Force-Iraq, arrives Wednesday to testify before the House of Representatives Armed Services Committee.

Gen. Ray Odierno said security has continued to improve in the three months since American forces withdrew from cities as part of a agreement to remove all American forces by the end of 2011.

The level of attacks has dropped from 4,064 in August 2007 to 594 this August, Odierno told the House Armed Services Committee.

"We have already begun deliberately drawing down our forces — without sacrificing security," he said.

There are about 124,000 American troops in Iraq. By the end of this month 4,000 troops will leave, he said.

At the peak of President Bush's increase in troops in 2007, there were about 160,000 U.S. forces there.

Odierno said the U.S. has closed 100 bases and reduced the number of foreign contractors to 115,000, from 149,000 at beginning of this year.

He said that improved security allowed them to withdraw forces faster than anticipated.

The decision to withdraw 4,000 this month reflected improved security in Anbar, a Sunni Muslim region west of Baghdad, he said.

It was once one of the most violent regions.

The panel's chairman, Rep. Ike Skelton, said adjustments "in Iraq will not be easy for us or, I suspect, for the Iraqis." He called moving troops and equipment out of Iraq a large challenge.

"The war in Iraq is coming to a close, but my suspicion is that these transitions will take years to work through," Skelton, D-Mo., said in a statement released shortly before the hearing began.

In his eight-page statement, obtained in advance of the hearing, Odierno voiced cautious optimism about Iraq's future. But he warned of several looming problems as U.S. troops prepare to end combat missions by September 2010 and leave Iraq at the end of 2011.

Those problems include:

—"A clear security lapse," Odierno said, was evidenced by a pair of truck bombings Aug. 19 at Iraq's finance and foreign ministries, which killed about 100 people in Baghdad.

—A system of government that is accepted across what Odierno described as ethnic, sectarian and regional lines has yet to be agreed on. He described a power struggle between provincial officials and Baghdad and said long-standing tensions continue to stall progress between Arabs and Kurds.

As the January elections approach, military officials have identified Arab-Kurd tensions as one of the top concerns for potential violence, especially in contested territories in the oil-rich north that each side claims as its own. Still, Odierno said the darkest days of the Iraq war seem to be long gone, citing failed efforts by extremists still seeking to destabilize the nation.

"The overwhelming majority of the Iraqi people have rejected extremism," Odierno said. "We see no indications of a return to the sectarian violence that plagued Iraq in 2006-2007."

—Although Iraqi leaders had planned to find government jobs for all members of a group known as Sons of Iraq, who helped curb the insurgency, "we do not believe they will meet this timeline," Odierno said. "We continue to monitor the progress of this program very closely."

Iraq's government promised to open thousands of police and military jobs, dominated by Shiites, to the Sons of Iraq, who are mostly Sunni. But the government has been accused by Sunnis of dragging its feet on integrating the jobs.

Odierno, however, said 23,000 former Sons of Iraq have begun working in government jobs since 2008, and 5,000 more will start next month.

Contributing: Associated Press