Is modern Syria part of what-was ancient Mesopotamia way back then?

At least the eastern part of Syria was in Mesopotamia. Mesopotamia, in a literal sense, was the region between the Tigris and the Euphrates (from ancient greek: Meso (between) + potam�s (river). Mari, a clearly Mesopotamian kingdom, had its main city (Mari, now days Tell Hariri) about 11 Km of Abou Kemal, thus, in modern day Syria southeast, by the middle Euphrates.