The summit in the Turkish capital will deal with developments in Idlib, refugees and a political solution to the lingering conflict in Syria.
"It is aimed to evaluate the developments in Syria, especially in Idlib, to end the conflict environment, to provide the necessary conditions for the voluntary repatriation of refugees and to consult the joint steps to be taken in the future in order to establish a permanent political solution," the Turkish presidency had said in an earlier statement.
Speaking to reporters at the Mehrabad Airport in Tehran ahead of his visit to Ankara, Rouhani said Sunday that Syria's future belongs to its people.
"Apart from the stability and security of the region, I hope that Ankara's trilateral summit will take effective steps and that the three countries can agree to help the people and the future of Syria," he said.
"We have always emphasized that the future of Syria belongs to the people of this country, and other countries should help the Syrian people in this regard," Rouhani said.
He recalled that Monday's summit would be the fifth meeting of this format in the last two and a half years, underlining that the three countries "have been guarantors of the cease-fire in Syria".
Rouhani said combating terrorism and countering foreign interference in Syria, return of the Syrian refugees, reconstruction and constitutional reform, as well as elections in 2021 are among the important issues that will be discussed at the summit.
The Iranian president stated that there were still parts of Syria facing trouble, including the eastern Euphrates region and added that the illegal presence of the U.S. was disturbing peace in Syria.
He said the main concerns of the three guarantor states were the intervention and aggression of Israel in Syria and its support for the terrorists, and the regime's attacks on the Syrian people and infrastructure.
Rouhani went on to say that regional issues must to be resolved by regional countries through dialogue.
Rouhani said the U.S. was supporting Saudi Arabia and the UAE in Yemen by supplying them weapons. "If we want full security in the region, the U.S. intervention should stop."
Rouhani also said Iran's relations with Russia and Turkey were "very friendly."
"We are ready to have friendly relations with all our neighbors. The best way to resolve our country's economic problems is to have close economic ties with our neighbors," he concluded.
The summit on Monday is a follow-up of the landmark Astana talks on Syria.
The Astana peace process aimed at ending the Syrian conflict was launched in January 2017 by Russia, Iran and Turkey. So far 13 rounds of talks have been conducted in Astana, Kazakhstan.
Turkey and Russia agreed last September to turn Idlib into a de-escalation zone where acts of aggression are expressly prohibited.
The Syrian regime and its allies, however, have consistently broken the terms of the cease-fire, launching frequent attacks inside the de-escalation zone.
The zone is currently inhabited by about 4 million civilians, including hundreds of thousands of people displaced in recent years by regime forces from cities and towns throughout the war-weary country.
