'Hundreds of thousands of people could be killed.
Zarif made a surprise visit to Syria on Monday for talks on the Assad regime's looming offensive against the country's last major opposition stronghold, his ministry said. Don't let that happen!'
More than seven years since the conflict began, regime forces have managed to retake entire regions from rebels and militants, and now control almost two-thirds of the country.
Iranian Foreign Minister Mohammad Javad Zarif visited Damascus to discuss plans for an upcoming summit between the leaders of Iran, Russia and Turkey, which Tehran will host on September 7 to discuss Idlib, Iran's Fars news agency reported.
"All of Syrian territory must be preserved and all the sects and groups should start the round of reconstruction as one collective and the displaced should return to their families", Zarif said, according to Fars.
Syrian government forces are now massing around the northwestern province of Idlib, which is held by a complex array of rebels and violent extremist fighters, many of whom have been blacklisted as "terrorists" by world powers.
Last week Iran and Syria signed a treaty making provision for Iranian engineers to play a role in reconstructing the Syrian military industry.
Tehran has provided steady political, financial and military backing to Assad as he has fought back a seven-year uprising.
The President's warning comes just days after Secretary of State Mike Pompeo issued a similar warning to Russia's foreign minister, Sergey Lavrov, saying an attack on Idlib was something that Syria and Russian Federation "agreed not to permit", and that the U.S. "sees this as an escalation of an already unsafe conflict".
The attack killed at least 8 of the Iranian force and the militia gunmen-1 Iranian, 3 Syrians and 4 "others", and injured at least 11. Israeli Prime Minister Benjamin Netanyahu responded to the attacks stating, "we will not stop taking action in Syria against Iran's attempts to establish a military presence there".