US President Barack Obama said on Wednesday that the problems in Syria cannot be resolved without support and participation from Russia, Turkey and Iran.
He added that other partners should also contribute to the discussions.
"In order for us to resolve it, there is going to have to be agreement among the major powers that are interested in Syria that this is not going to be won on the battlefield," Obama said.
Iran and Russia openly support the Bashar al Assad regime since the beginning of the Syrian civil war in 2011.
Turkey, on the other hand, has frequently condemned Assad’s offensives against opposition fighters, and his attacks on civilians which led to the flee of millions.
More than 220,000 Syrians have been killed so far and more than a million wounded in the country’s four-year civil war since March 2011, according to UN estimates.
At least 5 million have fled the country to neighbouring Turkey, Iraq, Lebanon and Jordan.
The number of Syrians who have asked for asylum in Europe has reached 270,000, with 7.6 million Syrians, about 70 percent of the country’s population are displaced within Syria.
About 86 percent of Syrian refugees in Jordan, around 630,000 people, live below the international poverty line of $3.2 per day, the UNHCR statement said. More than half of the 1.173 million Syrians in Lebanon live in substandard shelters.
Turkey, which hosts the largest number of refugees in the world, provides refuge for an estimated 1.8 million Syrian refugees - including around 200,000 from Kobane - more than any of Syria’s other neighbours.