BAGHDAD, Iraq (CNN) -- The commander of U.S. forces in northern Iraq said on Friday that because security has improved in the region, the military might be able to reduce the U.S. troop level there by half over the next two years, starting in January.
U.S. Army Maj. Gen. Benjamin R. Mixon, speaking to reporters via teleconference, said that more cooperation from tribal leaders -- and in some cases from insurgent groups that oppose al Qaeda in Iraq -- has helped improve conditions in northern Iraq.
Mixon did not address the issue of where troops might go if they were to be taken out of the northern region of the country.
Still, most of the insurgents his troops are fighting are Iraqis, Mixon said.
When the U.S. refers to capturing or killing members of al Qaeda in Iraq, it is generally referring to Iraqis who have "linked themselves with the al Qaeda ideology," Mixon said.
He said only "a very small number of foreign fighters" were among the 90 al Qaeda operatives killed and 130 captured in Operation Arrowhead Ripper, a three-week-old joint U.S.-Iraqi campaign against an insurgent hotbed in Baquba.
Mixon credited one Sunni Muslim insurgent group -- the 1920 Revolution Brigades -- with providing key intelligence information that helped minimize U.S. casualties in Operation Arrowhead Ripper. One U.S. soldier was killed by a roadside bomb during the operation, which began on June 19, Mixon said.
Mixon said that while Iraqi troops at lower tactical levels are proving trustworthy and effective, his main concern is improving the higher level command and control structure for the Iraqi security forces.
The overall improvement, Mixon said, has led him to recommend that Iraqi forces take over responsibility for security in one of the provinces in his command -- Nineveh, along the Syrian border.
U.S. troops would still be in the province to assist the Iraqis, but eventually their numbers could be drawn down, he said. The number of American troops has already been cut in half in Nineveh province in the last 18 months, he said.
"We believe that we are making a difference and the full effects of the surge are now being realized," Mixon said.
Also Friday, a reporter for the New York Times in Baghdad was shot to death on his way to work, according to the newspaper's Baghdad bureau and Iraq's Interior Ministry.
Khalid W. Hassan, a 23-year-old Iraqi who had worked for the Times' Baghdad bureau for four years, "was a resourceful and brave member of our news team, who met the many professional and personal challenges of his four years on our staff with enduring good humor and optimism," said John Burns, the bureau chief.
Iraqi police reported finding six bullet-riddled bodies, including those of two women and an 11-year-old girl, Friday afternoon in the same area where Hassan was killed.
Hassan's death came a day after two Iraqis working for the Reuters news agency were killed in the same Shiite neighborhood by crossfire between U.S. troops and Iraqi insurgents.
According to the count kept by the New York-based Committee to Protect Journalists, 110 journalists and 40 media support staffers have been killed in Iraq since the U.S.-led invasion in March 2003. The CPJ estimates more than 80 percent of those killed have been Iraqis.
Meanwhile, an Iraqi police officer who is "suspected of coordinating logistical support from Iran" was detained on Friday in a coalition raid in Baghdad, the U.S. military said.
Coalition and Iraqi security forces battled insurgents in the raid, an engagement that led to several deaths -- seven insurgents and six Iraqi police officers, according to initial reports.
Coalition forces -- long concerned about the presence of death squad and militia members in security forces -- came under fire from an Iraqi police checkpoint during the raid. The U.S. military said it is urgently investigating whether the fire came from actual police, or from militants in stolen uniforms.
The detainee is suspected of directing roadside bomb and indirect fire attacks against coalition forces, the military said. "The detainee is believed to have close ties to the Iranian Revolutionary Guards Corps' Quds force," the statement added.
CNN's Mohammed Tawfeeq and Saad Abedine contributed to this report.