The Iraqi government insisted that it's not up to the United States to negotiate over Iraq's security with Syria as a delegation from the Obama administration arrived Wednesday in Damascus.

Prime Minister Nouri al-Maliki will make his own trip to Syria next week to discuss security, the government said, calling the issue an internal Iraqi affair. U.S. and Iraqi officials have long been concerned about the infiltration of foreign fighters across the Syrian border.

"It is not the duty of the American delegation to negotiate on behalf of Iraq," spokesman Ali al-Dabbagh told The Associated Press. "It is the Iraqi government that will directly negotiate on security with Syria."

The remarks underscored emerging strains in the relationship between the Iraqis and the Americans as the balance of power shifts with the impending withdrawal of U.S. forces by the end of 2011. U.S. combat forces already turned over urban security to Iraqi forces on June 30, focusing their efforts on the borders and rural areas.

U.S. officials dismissed concerns about a rift over this week's talks in Damascus, which also were expected to deal with prospects for Mideast peacemaking.

"One of the issues that we continue to discuss with Syria is its efforts in terms of taking care of border issues on the Syrian side of the border," State Department spokesman P.J. Crowley said. "We have had concerns, going back a number of years, regarding the infiltration of foreign influences from the region through Syria into Iraq."

And, Crowley said, Iraq benefits from the effort to deal with the problem.

The mostly military delegation includes Frederic Hof, an assistant to George Mitchell, a former Senate Democratic leader who oversees U.S. Mideast peacemaking efforts. An earlier round of talks was held in June. Hof has been rumored to be in line for nomination as U.S. ambassador to Damascus. The post has been vacant for four years.

The talks are part of an acceleration of U.S. engagement with the Arab world and U.S. hopes that Syria can play a constructive role.

But Crowley said Tuesday that the infiltration of foreign fighters from Syria into Iraq would be "a significant topic of discussion."

U.S. and Iraqi officials have sought to shut down Sunni extremist networks that smuggle weapons and fighters through Iraq's northern desert to Mosul, where Al Qaeda and other Sunni insurgents remain active.

American special forces staged a cross-border raid in October that Washington said killed the Al Qaeda-linked head of a Syrian network that smuggled fighters, weapons and cash into Iraq. The operation outraged Syria, which claimed only civilians were killed.

The some 130,000 remaining U.S. troops face new limits on their actions in Iraq under a security pact that took effect on Jan. 1, and the Iraqi government has increasingly been asserting its sovereignty and reaching out to neighboring countries.

Al-Maliki's trip comes as violence has risen over the past week with a series of devastating bombings that have killed more than 120 people.

Gunmen also assassinated a senior Iraqi police officer late Tuesday as he was leaving a funeral in his hometown near Mosul, authorities said.

Brig. Gen. Abdul-Hamid Khalaf, a 55-year-old father of three, was an army officer under Saddam Hussein's regime but joined the police force amid efforts to rebuild the Iraqi security forces following the 2003 U.S. invasion.

He was a provincial police spokesman from 2005 to 2007, when he was promoted to be the deputy head of emergency battalions, and had survived at least one other attempt on his life.

The officer was killed by a gunman while walking home from a funeral service for a fellow officer who had died of natural causes in Zawiya, a mainly Sunni village and former Al Qaeda in Iraq stronghold 45 miles south of Mosul, according to the area's police chief, Brig. Gen. Khalil al-Jubouri.

Elsewhere in northern Iraq, a roadside bomb killed a policeman and wounded five people Wednesday in the disputed oil-rich city of Kirkuk, police said. Three other policemen were later killed while dismantling a parked car bomb in the northern city.

A bomb attached to the car of an employee of a cell phone employee also exploded, killing him and seriously wounding a colleague in Mosul, according to the provincial police.