By Mark Hosenball and Phil Stewart
WASHINGTON, June 26 (Reuters) - U.S. intelligence about the Islamist insurgent offensive in Iraq is improving but it could take weeks to complete a detailed picture of the threat and any possible American air attacks do not appear imminent, U.S. officials said on Thursday.
Last week's announcement that up to 300 U.S. military advisers were being sent to Baghdad and the earlier movement of an aircraft carrier, a cruiser and a destroyer into the Gulf prompted speculation of impending military action against Islamic State of Iraq and the Levant (ISIL) militants.
"We're just not there yet," one official told Reuters, speaking on condition of anonymity.
The U.S. intelligence picture is being filled in with information from flights by about 30 to 35 manned surveillance planes and drones flying over the country daily.
U.S. officials said this would be further boosted by the opening on Wednesday of a joint Iraq-U.S. operations center in Baghdad staffed by about 90 military personnel.
It will take time, the officials said, to build a detailed picture of ISIL's deployments, intentions and weapons stockpile, which has grown considerably since its black-clad forces overran Iraqi government arsenals in the last few weeks.
Another U.S. official, who declined to be identified, said the patchy nature of current intelligence on ISIL's activities would not necessarily rule out early limited U.S. air strikes should specific targets be identified.
President Barack Obama has been reluctant to engage in the sectarian conflict. The president has said the emphasis at this stage is on pressuring the Shi'ite-dominated leadership in Baghdad to build an inclusive government that brings in Sunni and Kurdish factions to create a united front ISIL's Sunni fighters.
Members of Congress, who would have to approve action if it became long or expensive, have made clear that they would back action only if they see concrete signs that Iraqi Prime Minister Nuri al-Maliki is moving to form an inclusive government.
Democratic Senator Carl Levin, chairman of the Armed Services Committee, on Thursday set three conditions for his support for direct U.S. involvement, including air strikes.
He said he would back them if U.S. military leaders thought they would change the momentum on the ground, if they were supported by U.S. allies in the region and if leaders of all elements of Iraqi society came together to make a formal request for more direct support.
In a speech in the U.S. Senate, Levin criticized Maliki as failing to take action to draw in other factions and said: "We can't save Iraqis from themselves. Only if Iraq's leaders begin to unify their nation can any help from us really matter."
U.S. officials in Washington said as well as U.S. surveillance flights, aircraft from Iran and Syria, both U.S. adversaries but Shi'ite-run states supportive of Maliki, may also be flying over Iraq.
Syrian and Iraqi officials said Syrian aircraft hit the town of Al-Qaim on their mutual border. Malaki said the strike took place within Syrian territory and there was no direct coordination.
The State Department said it had no evidence to counter reports that Syrian planes had struck ISIL targets inside Iraq. A U.S. official said there was evidence that Iranian surveillance drones were operating over eastern Iraqi airspace, perhaps flying from within Iraq. (Additional reporting by Peter Apps; Editing by David Storey and David Gregorio)