The alliance calling itself the Democratic Forces of Syria includes the Kurdish YPG [from the Kurdish initials for People's Protection Units] militia and Syrian Arab groups, some of which fought alongside it in a campaign that drove Islamic State from wide areas of northern Syria earlier this year, Reuters wrote.
The Arab groups in the new alliance are operating under the name "The Syrian Arab Coalition" – a grouping which U.S. officials have said would receive support under a new U.S. strategy aimed at fighting Islamic State in Syria.
A spokesman for some of the Arab rebels said they were told by Washington that new weapons were being sent to help them launch a joint offensive on the city of Raqqa.
"We met the Americans and this has been approved and we have been told these new arms ... are on their way," said Abu Muazz, a spokesman for the Raqqa Revolutionaries Front, a grouping of mainly Arab tribal insurgents who are mostly drawn from the Raqqa area.
He said the group constituted a 3,200-strong, well trained fighting force which could begin using the weapons within days of their arrival. It has an additional 600 fighters who are currently wounded, he said.
A major offensive against the ultra-hardline Islamic State fighters could capture Raqqa in less than two months provided the "right weapons and quantities" arrived, Abu Muazz, himself from the jihadist-held city, said without elaborating.
A U.S. military official has told Reuters that the Syrian Arab Coalition would push down towards Raqqa, Islamic State's de facto capital, while staying east of the Euphrates river.
