Iran's foreign minister in Damascus as Idlib offensive looms
Zarif met his counterpart Walid al-Muallem according to the Syrian foreign ministry's Facebook page, and is scheduled to meet President Bashar al-Assad on the one-day trip, according to Iranian media.
The surprise talks come as the regime, backed by Iran, is expected to launch a phased offensive in the northwestern province of Idlib and surrounding areas, the last big rebel enclave.
"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 News.
"And the remaining terrorists in the remaining parts of Idlib must be cleaned out and the region should be placed back under the control of the Syrian people," he added.
The meeting follows the minister's surprise talks with Turkey's President Recep Tayyip Erdogan last week.
While Iran's forces back Assad's regime, Ankara has throughout the seven-year civil war in Syria supported rebels seeking to oust Assad.
However it has recently put differences aside to form a three-way alliance with Tehran and Moscow, another key regime ally.
An assault on Idlib province could test the alliance of the regime allies with Turkey, as Ankara warns a military solution could lead to catastrophe and a new influx of refugees across its borders.
Turkey has 12 military observation posts inside Idlib aimed at monitoring a de-escalation zone and media reports have said it has sent concrete blocks over the border to reinforce them in case of an assault.
Iran's Revolutionary Guard is a key player in Syria, having flooded the country with foreign militias.
The quasi-paramilitary force also operates thousands of companies - including construction enterprises - that helps the Guard retain a powerful hold over domestic politics.
Tehran and Damascus have had strong ties for years. Iran has dispatched military forces to Syria, describing them as "advisors". Last week it signed a military cooperation and reconstruction deal with Syria, extending its influence in the war-torn country.
Erdogan and his counterparts Hassan Rouhani of Iran and Russia's Vladimir Putin are due to meet in Iran for a third summit on Syria on 7 September, Turkish reports and Iran's Fars News have said.
"I'm optimistic that this meeting will be successful and productive for the region, the people of Syria and the fight against terrorism," foreign ministry spokesman Bahram Qassemi said on Monday.
"One of the complicated issues today is Idlib which is the last stronghold of anti-government insurgents," Qassemi said. "The government of Syria is determined to put an end to this catastrophe."
"The government of Syria has the right to fight against terrorists in this region. And Iran, as a supporter of the Syrian government, is present and will continue its advisory help as long as the Syrian government wants."
According to independent monitors, hundreds of thousands of civilians have been killed in Syria's bloody conflict, and millions have been displaced both inside and outside of Syria.
The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations.