WASHINGTON - The United States and Iraq agreed on Thursday to boost cooperation to keep Iran from flying weapons over Iraq to Syria, and to curb the radicalization of young Iraqis and other spillover effects from the Syrian conflict.US help for Iraq will include intelligence- and information-sharing in the short term, followed by a planned sale of a $2.6 billion integrated air defense system and F-16 fighter jets, a senior US official said.MILITANT INFILTRATION PLUS LOCAL DISCONTENTThe Iraqis had stressed in the talks the difficulty they had monitoring and controlling their airspace and the US assistance is aimed at easing this problem.The US Defense Security Cooperation Agency notified Congress on Aug. 5 of plans to sell Iraq an Integrated Air Defense System that includes radar, missiles, guidance systems, training and support. Iraq will receive a shipment of F-16s in autumn 2014 and pilots are undergoing training, the US official said.The official quoted Kerry as telling the Iraqis that the leadership of al-Qaida in Iraq had moved to Syria and "they are flush with jihadi recruits that are coming into Syria and we think they are sending a number of them into Iraq."Evidence that suggests an al-Qaida infiltration in Iraq includes a spike in suicide bomb attacks from 5-10 per month in 2011 and 2012 to almost 30 a month in the past 90 days, most suspected as coming from Syria, US officials said.Zebari said after his talks with Kerry that no Iraqi militants were going to Syria with the consent of the Iraqi government and the US official said Washington agreed that this was the case.Kerry told Zebari Iraqi Prime Minister Nuri al-Maliki's government must also address festering political and economic problems that alienate the Sunni minority in Iraq, including by passing stalled economic legislation, the senior US official said."If the Sunni population in Iraq feels totally discontented, then there's an environment for extremists to take advantage," the official said.The agreement came during talks in Washington led by Secretary of State John Kerry and Iraqi Foreign Minister Hoshiyar Zebari, which took place amid a period of escalating bloodshed that has taken the monthly death toll in Iraq to its highest levels in five years.Car bombs in Baghdad killed at least 34 people on Thursday, underlining the revival of a Sunni Muslim insurgency that analysts say has been energized by the Syrian conflict and the failure of Iraqi politicians to overcome sectarian divisions.The US and Iraqi diplomats discussed the impact of Syria's civil war, raging since March 2011, and political issues behind the growing Sunni insurgency, including that by al-Qaida, against Iraq's Shi'ite-led government, the US official said.US officials have long complained that Shi'ite Iran, which has considerable influence in Iraq, has used Iraqi airspace to ferry weapons to the government of Syrian President Bashar Assad, which Tehran backs.Kerry said Iraq had made some progress in dealing with this problem and the flow of weapons from Syria back into Iraq since he visited Baghdad in March, but greater efforts were needed."It's a two-way street and it's a dangerous street," Kerry said.The senior US official said that in the six months prior to Kerry's trip, there were no Iraqi inspections of overflights to Syria from Iran."From March until now, the record has been quite different and we have seen a disruption in the flow of what we suspect is cargo going from Iran to Syria," said the official.However, the official acknowledged that while the frequency of suspected Iranian overflights of Iraq was down, the Iraqis had not actually intercepted any weapons and much work still needed to be done.