China exports an older style S-300 which Israel can jam, unlike Russia S-300/400 systems. The problem is with upgrade to radar it maybe harder to jam and Iran is making it own SA-20 missiles which more than doubles older S-300s range. 2 are known to be in operation now.
U.S. to defend Syrian rebels with airpower, including from Assad (Reuters)
from the article: Russia to freeze missile sale to Iran, Putin tells Sarkozy