Syria's President Bashar Assad has said his government has been receiving general messages from the American military about air strikes targeting the Islamic State group inside Syria, but there is no direct co-ordination.
In an interview with the BBC aired today, Mr Assad said the messages are conveyed through third parties, such as Iraq.
"Sometimes they convey message, general message, but there's nothing tactical," he said.
A US-led coalition is carrying out air strikes in Syria as part of an international campaign against Islamic State extremists.
They share the skies with Mr Assad's air force, which is also targeting the militants.
In the interview, Mr Assad denies his forces have used barrel bombs.
The government's use of the crude explosive devices, usually dropped by helicopters, has been widely documented by international human rights organisations.