(Corrects headline to change attacks to attack) By Kristin Roberts WASHINGTON, March 20 (Reuters) - A U.S. general on Tuesday said Iraqi insurgents used children in a suicide attack this weekend, raising worries that the insurgency has adopted a new tactic to get through security checkpoints with bombs. Maj. Gen. Michael Barbero, deputy director for regional operations in the Joint Staff at the Pentagon, said adults in a vehicle with two children in the backseat were allowed through a Baghdad checkpoint. The adults then abandoned the vehicle and detonated it with the children still inside, he said. "Children in the back seat, lower suspicion, we let it move through," he said. "They parked the vehicle, the adults run out and detonate it with the children in the back." "The brutality and ruthless nature of this enemy hasn't changed," Barbero said. The general called that incident a new tactic, but noted U.S. forces had only seen one such occurrence involving children. The use of chemical bombings has increased and become a tool of the insurgency, as the three chlorine bombs detonated this past weekend brought the total to six such bombings since January, the general said. "High-profile" suicide and car bomb attacks by Sunnis against Shi'ites also have not abated, Barbero said. But he said increased force in Iraq's capital had yielded some success, such as a reduction in murders and executions of civilians. He also said hundreds of families have returned to Baghdad and the number of tips from Iraqi civilians about insurgent activity hit its highest mark ever in February. TIMELINE TO WITHDRAW Barbero's comments come as Congress considers measures that attempt to force a timeline on the Bush administration to withdraw U.S. troops. The general said improving security will "take time and determination," and said: "We need to take a long term view." The United States has plans in place to send more than 21,500 additional troops to Baghdad and Anbar -- the most violent areas of Iraq. Many of the troops have already arrived and all of the U.S. brigades promised for Baghdad will be in place by June, as targeted, Barbero said. The aim of the increase, according to U.S. Defense Secretary Robert Gates and military officials, is to establish enough security to give Iraq's government "breathing room" to make political and economic progress. That strategy, however, has been criticized by some lawmakers in Washington. Rep. Ike Skelton, a Missouri Democrat who chairs the U.S. House of Representatives' Armed Services Committee, for example, said violence between Sunnis and Shi'ites will worsen when the United States leaves Iraq, regardless of when that pull-out occurs. "Should there be a redeployment now, six months from now, two years from now, the sectarian violence will increase," Skelton said on Tuesday. "It's inevitable." Asked about the Shi'ite militia led by radical cleric Moqtada al-Sadr, Barbero declined to say whether U.S. forces were in negotiations with the group. "I think where we are with the leaders of his movement's at a pretty delicate point and I probably don't want to talk any more about his followers, where we are in our relationship with them," Barbero said. "That's probably best left unsaid." But the general said U.S. and Iraqi forces were operating freely in Baghdad's Sadr City, a Shi'ite militia stronghold, and that he believed the cleric was still in Iran.
