Baghdad ? A suspected al-Qaida suicide bomber rammed a speeding gasoline truck into an Iraqi army checkpoint Saturday outside the capital, killing at least 14 soldiers as militants hammered the country’s shaky security forces.

The terror campaign against Iraqi troops and police appears designed to blunt U.S. progress in creating a stable local force so the Americans can go home. U.S. military officers began noticing the new pattern of attacks last month.

The focus on Iraqi forces was detailed to Maj. Gen. Joseph F. Fil Jr., commander of the 1st Cavalry Division, which runs the nearly four-month-old security operation in Baghdad, during a recent visit to the capital’s Karradah district.

Lt. Col. Troy D. Perry, the battalion commander in the area, told Fil there was an increasing pattern of bombers allowing U.S. patrols to pass hidden roadside bombs that were then detonated a short time later as Iraqi forces drove by.

Fil and Perry speculated al-Qaida was focusing on Iraqi forces to unnerve the soldiers and police who are working with U.S. forces to clamp off violence in the capital.

“Al-Qaida is the biggest problem you’ve got right now,” Fil said in a brief meeting with Iraqi army 1st Lt. Ziad Tariq, at an Iraqi base adjacent to the U.S. joint security station in Karradah late last month.

In Iraq’s first confirmation of Turkey’s cross-border shelling of Kurdish regions in the north of the country, the Foreign Ministry summoned the second-ranking Turkish diplomat to protest and demand an end to the attacks.

The shelling served to “undermine confidence between the two nations and negatively affect their friendship,” according to an account posted on the Foreign Ministry Web site.

Turkey has massed troops along the Iraq border and there has been scattered shelling of suspected separatist enclaves in Iraq’s Kurdish-controlled regions in the north. There were unconfirmed and conflicting reports that Turkish soldiers had crossed the border in “hot pursuit” of Kurdish rebels late last week. The Kurdish fighters have waged a bloody secessionist campaign in southeastern Turkey since 1984.