WASHINGTON - There is "lots of evidence" that chemical weapons are being prepared by Syria n government forces in Idlib region in northwest Syria , the new US representative for Syria said on Thursday, warning any attack on the last big rebel enclave would be a "reckless escalation."

"Any offensive is to us objectionable as a reckless escalation," the envoy, Jim Jeffrey, told reporters. "There is lots of evidence that chemical weapons are being prepared."