An offensive to capture the Syrian city of Raqqa from Daesh has officially begun, the US-backed Syrian Democratic Forces (SDF) announced on Sunday.
"The major battle to liberate Raqqa and its surroundings has begun," Jehan Sheikh Ahmed, a spokeswoman for the SDF, said at a press conference in Ain Issa, some 50 kilometres (30 miles) north of Raqqa.
The SDF, an alliance of Kurdish and Arab fighters led by the YPG, has been supported by US air power in the operation against Daesh in Syria.
Raqqa is Daesh's self-proclaimed capital in Syria, and the offensive to free the city comes at a time when similar push is underway against the in Mosul, Iraq.
Mosul is considered one of the last remaining strongholds of Daesh in Iraq.
Capturing the two cities, both still home to large civilian populations, is expected to be a lengthy process.
The announcement of the Raqqa offensive comes despite Turkey's concerns over the presence of YPG in the SDF ranks.
The YPG is considered by Turkey as an offshoot of the PKK, which has been designated as a terrorist group by Ankara, the EU and the US.
The PKK has been waging an insurgency inside Turkey since 1984.
"Turkey will not allow any development in Syria, Raqqa and Mosul which could threaten Turkey's security," said Fikri Isik, Turkey's Minister of National Defence, in response to Sunday's development.
"For this reason, we have taken every precaution, and we will continue to take every precaution. All options are on the table right now and will stay there."
Turkey's top leadership, including President Recep Tayyip Erdogan and Prime Minister Binali Yildirim, have repeatedly said that Turkish forces were ready to join the operation against Daesh in Raqqa, but that they would not fight alongside "terrorist groups like YPG".
In October, Turkey's deputy Prime Minister, Numan Kurtulmus, also said "it would be better both militarily and strategically to conduct this operation after the Mosul operation and Turkey's Euphrates Shield operation are completed."
Turkey launched an operation inside Syria on August 24 alongside allied opposition forces who have managed to retake the Daesh stronghold of Jarabulus and the symbolically important town of Dabiq.
Heads of Turkish and US militaries meet
On Sunday, the chief of general staff of the Turkish Armed Forces met with his US counterpart in Ankara on the request of the US military, the Turkish armed forces said in a statement.
There was official confirmation from president Barack Obama's envoy to the US-led coalition battling Daesh that the meeting revolved around the Raqqa offensive.
"We are in close close contact with our Turkish allies and that is why the chairman of joint chiefs is in Ankara today," special envoy Brett McGurk told a news conference in the Jordanian capital Amman.