Iraqi Prime Minister Nouri al-Maliki is in Damascus Tuesday for security talks with Syrian President Bashar al-Assad.
The United States and Iraq have sought to stop Sunni extremists who have been smuggling weapons and fighters into Iraq through Syria's border with Iraq's northern dessert. The smugglers are fueling attacks in Iraq's northern city of Mosul, which is considered a Sunni insurgent stronghold.
Last week a U.S. security delegation traveled to Syria for talks on Syrian efforts to help curb the movement of foreign fighters into Iraq.
U.S. State Department spokesman P.J. Crowley said such infiltration has affected Iraq's stability.
The Obama administration has been working to improve relations with Syria and advance the Middle East peace process.
The U.S. announced in June it plans to reinstate its ambassador to Syria after a four-year absence.
Some information for this report was provided by AFP and AP.