If Syrian President Bashar al-Assad stays in power, "I don’t think any refugee will go back," Ahmet Davutoglu told CNN.
In recent weeks, some Western diplomats have appeared to soften their position on Assad. They agree he must go, a senior U.S. diplomat has said, but they are open to having Assad stay for a transitional period.
Davutoglu dismissed the idea, saying, "The question is not how and how long Assad will stay, the question is when and how Assad will go.
"What is a solution? A solution is very clear. When, one day ... millions of Syrian refugees decide to go back to Syria, assuming that there is a peace in Syria, then this is a solution. If Assad stays in power in Damascus, I don’t think any refugee will go back.
"There is a need of a ... stage-by-stage strategy. But what is the endgame? What is the light at the end of the tunnel? That is more important for the refugees and people of Syria."
Most of the 744,000 migrants who have arrived in Europe by sea this year are from Syria, according to the United Nations Refugee Agency.
More than a million refugees have spilled over the Syrian border into Turkey, which has spent more than $7.5 billion caring for them, the Turkish president said last month.
"Crime against humanity"
In a wide-ranging interview, Davutoglu also called for ground troops to fight the ISIS terrorist group and safe havens for Syrian civilians on the country’s Turkish border.
He described the downing of a Russian passenger jet over Egypt’s Sinai Peninsula on October 31 as "an attack against all of us."
ISIS’ affiliate in Egypt says it brought down Metrojet Flight 9268, and U.S. officials say they are increasingly confident it was a terrorist bombing.
All 224 people on board were killed.
Davutoglu said the failure to contain Syria’s four-year civil war was to blame: "It shows that if a crisis is not being solved in a particular country or region, it is difficult to contain it in other countries as well."
He called for "safe havens" on Syria’s Turkish border and ground troops to fight ISIS, also known as ISIL.
"A ground force is something which we have to talk (about) together," he said. "There’s a need of an integrated strategy including air campaign and ground troops. But Turkey alone cannot take all this burden. If there is a coalition and a very well designed integrated strategy, Turkey is ready to take part in all senses."
But he warned that the integrated strategy is key.
"Otherwise, just to make a ground attack against ISIL, but continue to have a power vacuum on the ground instead of ISIL, another terrorist group may emerge."