The U.S. and France have warned an Idlib offensive would trigger a humanitarian crisis and warned that a chemical attack in Idlib would prompt a western retaliation.
The Mazzeh airbase houses Syrian Air Force intelligence, and in early 2017 the Syrian regime accused its neighbour Israel of bombing the base.
What could happen in Idlib?
Syria's foreign ministry and Iran's state-run IRNA news agency said Mohammad Javad Zarif was received by Deputy Foreign Minister Faisal Mekdad upon his arrival in Damascus, and was to meet later with Syrian President Bashar Assad.
Britain, France and the USA, which together launched limited attacks on Syrian installations in mid-April in retaliation for an alleged Syrian chemical attack, say their red line against illegal weapon use remains in force.
United Nations envoy to Syria Staffan de Mistura has warned of a "perfect storm" if the government goes ahead with its threatened offensive in Idlib.
Russia, which has yet to comment on the latest statement from the USA leader, has been working for weeks to establish humanitarian corridors in Idlib province.
"There is a flawless storm based on warnings, counter-warnings which is gathering around and due to the dilemma, which is a true dilemma on how to defeat terrorists in Idlib and at the same time avoid affecting a huge number of civilians", he said.
Overnight Saturday, a string of explosions at a military airport near the Syrian capital reportedly killed two regime fighters and injured 11 others.
Iran is voicing support for an impending Syrian offensive to recapture the last remaining major opposition stronghold, saying the Idlib region in northwestern Syria should be cleared of "terrorists".
How costly has the civil war been?
Thousands of government troops have been surrounding the area, preparing for what appears to be a major assault.
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.
Russian Federation and Iran, which support Assad, and Turkey have been in close cooperation over Syria in order to find a solution to the conflict.