Russian President Vladimir Putin has rejected Turkey’s calls for a truce to prevent a “bloodbath” in Syria’s Idlib.
At a trilateral meeting with Iran and Turkey, Mr Putin said that Russia would continue its fight against “terrorists” in the northern province.
Idlib is the Syrian opposition’s last major stronghold, with almost three million residents.
There are fears that a major Syrian government offensive, backed by Russia and Iran, is about to take place there.
During the meeting in Tehran, Iranian President Hassan Rouhani also spoke of “fighting terrorism” in the province but said civilians must not be made to suffer.
New air strikes on rebel positions in Idlib were reported on Friday morning.
Earlier, the new US envoy for Syria said there was “evidence” that Syrian government forces were preparing to use chemical weapons.
Why are these countries involved?
Iran, Russia and Turkey have played central roles in the Syrian conflict.
Turkey – which has long backed some rebel groups – fears an all-out assault will trigger another major refugee crisis on its southern border.
Russia and Iran – which have provided vital support for Syrian President Bashar al-Assad – believe jihadist groups in Idlib must be wiped out.
Russian planes have bombed rebel areas in the north-western region as Syrian government troops mass for the expected offensive.
What was said at the summit?
“Fighting terrorism in Idlib is an unavoidable part of the mission of restoring peace and stability to Syria,” Mr Rouhani told his Russian and Turkish counterparts.
“But this battle must not cause civilians to suffer or lead to a scorched earth policy.”
Russian President Vladimir Putin insisted at the trilateral meeting “the legitimate Syrian government has a right and must eventually take under control of its entire national territory”.
Turkish President Recep Tayyip Erdogan told the summit that this was the last chance to avert a bloodbath in the province, home to some three million people.
Their joint statement, however, contained no concrete measures on Idlib.
What did the new US envoy for Syria say?
Jim Jeffrey said the anticipated conflict would be a “reckless escalation”.
“I am very sure that we have very, very good grounds to be making these warnings,” Mr Jeffrey said in his first interview since being appointed.
“Any offensive is to us objectionable as a reckless escalation. There is lots of evidence that chemical weapons are being prepared.”
He did not give details of the evidence he was referring to.
Mr Jeffrey said a “major diplomatic initiative” was now needed to end the seven-year civil war.
He said there was “a new commitment” by President Donald Trump to remain involved in Syria until the Islamic State group (IS) was defeated and to ensure that Iranian fighters leave the country.
Mr Jeffrey said President Assad had “no future as a ruler” in Syria, but it was not Washington’s job to oust him. He said the US would work with Russia on a political transition.
What do we know of chemical weapons use?
The UN envoy to Syria, Staffan de Mistura, said last week that both the Syrian government and rebels had the ability to make chlorine-based chemical weapons
The Syrian government has repeatedly denied ever using chemical weapons.
Despite the denials, experts from the UN and the Organisation for the Prohibition of Chemical Weapons (OPCW) have said they are confident government forces were behind an attack involving the nerve agent Sarin on a rebel-held town in southern Idlib in April 2017 that killed more than 80 people.
The US state department warned on Monday that Washington would respond to any new chemical attacks by the Syrian government or its allies.
What is the state of Idlib?
There are believed to be up to 30,000 rebel and jihadist fighters in Idlib.
The UN says the region is home to some 2.9 million people, including a million children.