The three presidents, whose countries' are key foreign players in Syria's long civil war, were speaking at a summit in Tehran aimed at charting a way to end the conflict.
The presidents of Iran and Russian Federation on Friday backed a military offensive to retake the last rebel-held area of Syria as Turkey's president pushed for a cease-fire, perhaps the final chance to avoid what activists warn will be a humanitarian disaster.
Eyewitnesses inside Idlib province have told ABC News that hundreds of people are already on the move as Russian air strikes have begun hitting rebel positions in recent days. It is home to some three million people - around half of them displaced from other parts of the country, according to the United Nations. Erdogan disagreed with Putin, saying that the return of refugees to Syria would only be possible after a new constitution is agreed and adopted, and an election held to form a new government.
"There are no civilians left at all in the targeted villages", Hasan Younis, a member of the White Helmets emergency medical team based in southern Idlib province, said to ABC News.
However, Putin responded that he opposed a ceasefire because Nusra Front and Islamic State militants located there were not part of peace talks.
The Turkish leader also urged the Syrian regime and its allies to avoid a bloodbath, but Putin insisted Damascus as "the legitimate Syrian government has a right and must eventually take under control all its national territory".
"The fact is that there are no representatives of the armed opposition here around this table".More news: Facebook, Twitter fall as they face US Congress
Idlib is one of the so-called "de-escalation" zones set up as a result of talks by Russia, Turkey and Iran past year as Damascus regained control of more of the country. It would be good.
He stressed the importance of continuing the fight against terrorism in Syria until the eradication of all terrorist groups in the country, particularly in the northwestern province of Idlib.
Iran's President Hassan Rouhani addresses a meeting focusing on Syria with his Russian and Turkish counterparts Vladimir Putin and Recep Tayyip Erdogan in Tehran on September 7, 2018.
An AFP correspondent in Idlib saw convoys of families heading north, towards areas closer to the border with Turkey and less exposed to the launch of a major offensive.
"Conditions have been made in Syria to take in up to a million of refugees".
"Any attack launched or to be launched on Idlib will result in a disaster, massacre and a very big humanitarian tragedy", he added. "They are fleeing to areas near Turkey where they hope to be safe from further aerial bombardment". "Turkey has filled its capacity to host refugees". "The United States will continue to target those who facilitate transactions with the murderous Assad regime and support ISIS".
Widely abhorred internationality for the brutal conduct of the war, Assad has largely reclaimed most of Syrian territory though much of it is ravaged.
Russia, Turkey and Iran are seeking to end violence in Syria and facilitate negotiations between its government and opposition groups, which agree to cease hostilities and seek a political transition for their country.