WASHINGTON Early reports show some reduction of violence in Syria since a cessation of hostilities brokered by the United States and Russia came into effect on Monday, U.S. Secretary of State John Kerry said.
"The earliest reports are that there is some reduction in violence as well as a few reports of fighting here and there though it is far too early to draw any definitive conclusions," Kerry told reporters at the State Department.
"There will undoubtedly be reports of violations here or there but that is the nature of the beginning of the ceasefire almost always," he added.
Kerry said humanitarian assistance needed to urgently start flowing, including in all areas of Aleppo. "I don't think I have to spell out how urgent this assistance is, in some cases literally the difference between life and death for tens of thousands of people," he added.
He cited a report by the Syrian Observatory for Human Rights which said major conflict zones in Syria were calm after a ceasefire took effect at 7 p.m. (1600 GMT) on Monday.
Kerry said once there was a sustained period of calm and increased humanitarian access over seven days, the United States and Russia would begin to coordinate military strikes.
"As soon as U.S.-Russia strikes begin then the Syrian regime will be prevented from flying combat missions over areas in which the legitimate opposition is present," Kerry said.
The United States has long said that Syrian President Bashar al-Assad's air force should be grounded, but in recent weeks appeared to back away from that call saying Assad's forces could strike in areas where al-Qaeda-linked groups and Islamic State operated and where the opposition groups were not present.
This would prevent government forces from bombing civilians or opposition groups while claiming they were targeting militant groups, Kerry added.
Kerry said the truce was designed to enable warring sides to resume negotiations on a political transition in Syria.
"This is designed to bring people to the table in Geneva," he added.
(Reporting by Lesley Wroughton; Editing by Chris Reese and James Dalgleish)