Kurdish-led forces have launched an offensive to capture the Syrian town of Manbij, a suspected supply route for the Islamic State of Iraq and the Levant (ISIL also known as ISIS) group to smuggle weapons in from Turkey.
The Syrian Democratic Forces (SDF), a US-backed coalition of armed groups led by the Kurdish People's Protection Units (YPG), was mobilising near Manbij in the northern province of Aleppo on Thursday, the AFP news agency reported.
In the past 24 hours, 18 coalition air strikes are reported to have targeted positions held by ISIL, also known as ISIS.
Jennifer Cafarella, a Syria analyst for the Institute for the Study of War in Washington DC, said if anti-ISIL fighters take Manbij and then Jarablus, that would sever ISIL's link with Turkey.
"Recapturing Manbij and ultimately advancing to Jarablus would disrupt but not eliminate ISIS's ability to resupply," she said.
The US-led coalition has long had its eye on the so-called Manbij pocket.
But an offensive on this mainly Arab region has run into opposition from Turkey, a key partner in the alliance.
The US sees the SDF - which is dominated by YPG - as the most effective ground force against ISIL in Syria.
The SDF was founded in Syria's mainly Kurdish northeastern region in October 2015, and is made up of at least 15 armed factions - mostly fighters from the YPG and the Free Syrian Army.
On Wednesday Pentagon officials stressed that the attack on Manbij was being led by the Arab component of the SDF.
Turkey regards the YPG as a branch of the Kurdistan Worker's Party (PKK), which has fought a three-decade armed campaign against the Turkish state.
Last week, footage of US special forces wearing YPG patches on their uniforms angered Turkey.
The US responded by telling these forces to stop wearing the badge, but insisted that US troops would continue to help the Kurdish fighters, saying they were taking on ISIL fighters efficiently.
READ MORE: In Raqqa, support ISIL or die
Over the past 10 days the SDF has also launched an offensive to retake Raqqa, the main ISIL stronghold in Syria.
ISIL has imposed strict rule in Raqqa - home to more than 220,000 people before the Syrian conflict - and committed atrocities against the civilian population since its takeover of the city more than two years ago.
As the fighting continues, the United Nations said it hopes to send aid to 11 besieged areas in Syria in the coming days. But it said more effort is needed to make sure other areas are opened up.
On Wednesday, humanitarian aid reached the rebel-held Syrian town of Daraya and Moadamiyah.
Syria's conflict started with mostly unarmed demonstrations against President Bashar al-Assad in March 2011.
It has since evolved into a full-on civil war that has killed at least 270,000 people, according to the UK-based Syrian Observatory for Human Rights.
Source: Al Jazeera and agencies