Speaking to reporters on Friday, Mattis said the possible attack would be a mistake.

We have stated that we would be a on a side of the operation and the Russians on the other side, he said about U.S.-Russia operational regions in Syria, adding that we are still defeating the Islamic State (IS) and nothing has changed.

He warned about crossing the line.

Mattis said a larger U.S. civilian presence including contractors and diplomats will be seen on the ground in Syria, as the fight against the (IS) militants nears its end and the focus turns toward rebuilding.

He said the United States is shifting from an “offensive terrain seizing approach to a stabilizing” in Syria.

“Well, when you bring in more diplomats, they are working that initial restoration of services, they bring in the contractors, that sort of thing,” Mattis added, Reuters reported.

He ultimately denied that the U.S. is seeking to divide Syria.

Reporter’s code: 50101