Members of US-backed Kurdish-Arab forces (of various nationalities) deploy on the frontline, some 50km north of Raqqa, on Sunday.

US Defense Secretary Ashton Carter has warned that the fight to wrest control of Raqqa, the Daesh stronghold in Syria, “will not be easy.” 
“The effort to isolate, and ultimately liberate, Raqqa marks the next step in our coalition campaign plan,” Carter said in a statement.
“As in Mosul, the fight will not be easy and there is hard work ahead, but it is necessary to end the fiction of Daesh’s caliphate and disrupt the group’s ability to carry out terror attacks against the US, our allies and our partners,” he said.
“The international coalition will continue to do what we can to enable local forces in both Iraq and Syria to deliver ISIL (Daesh) the lasting defeat it deserves,” the US defense chief added.
Carter issued his remarks as Kurdish-led Syrian forces backed by the US said they had begun a military campaign to liberate Raqqa from Daesh, urging civilians to avoid “enemy gatherings” in the Syrian city and warning Turkey not to interfere in the operation.
In Amman, a senior US official said Washington is in “close contact” with Ankara over the assault launched by Kurdish-Arab Syrian Democratic Forces (SDF).
“We are in close close contact with our Turkish allies and that is why the chairman of joint chiefs is in Ankara,” Brett McGurk, US President Barack Obama’s envoy to the US-led coalition battling Daesh, told a news conference in Amman.
“We want this to be as coordinated as possible, recognizing that there will be a mix of forces on the field and that many of those forces of course do not see eye to eye, but they do share a very common and still very lethal enemy,” he said of Daesh.
The SDF said earlier that Washington had agreed Turkey would play no role in the offensive.
Ankara had previously expressed alarm that the SDF were dominated by the Kurdish Peoples’ Protection Units (YPG) militia which it considers an offshoot of the Kurdistan Workers’ Party (PKK) that has waged an insurgency against Turkey for more than three decades.
“It is a complex environment in Syria to say the least, but we are constantly in touch with all the different players, and I think in terms of the phasing of the overall Raqqa campaign we have a fairly good understanding of what is to come,” said McGurk.
SDF commanders announced the start of the operation against Raqqa in Ain Issa, some 50 km north of the city.
“The major battle to liberate Raqqa and its surroundings has begun,” SDF spokeswoman Jihan Sheikh Ahmed said.
Operation “Wrath of the Euphrates” involves some 30,000 fighters and began on Saturday night, Ahmed said.
SDF forces are advancing on three fronts, from Ain Issa and Tal Abyad to the north of Raqqa, and from the village of Makman to the east.
SDF spokesman Talal Sello said that the operation would proceed in two phases, first seizing areas around Raqqa and isolating it, then taking the city itself.
An AFP correspondent in Ain Issa Sunday saw dozens of SDF fighters heading on vehicles toward the front line.
Ahmed told AFP in Beirut later that 10 villages and several hamlets had been retaken.
Daesh said it carried out a suicide car bombing in the Suluk area that killed 14 SDF fighters. 
Driving the terrorists from Mosul and Raqqa has been the endgame since the US-led coalition launched air strikes against the terrorists in the summer of 2014.

Source: Arab News