Kurdish fighters from the People's Protection Units (YPG) chat with members of US forces in the town of Darbasiya.
At least 23 forces of the US-backed Syrian Democratic Forces (SDF) were killed on Tuesday in a fight with the radical Islamist forces.
The Islamist State could not retain their last bastion in eastern Syria in the fight which also killed nine jihadists.
The Islamist forces used the cover of the bad weather and launched a deadly counterattack against the Kurdish-led force.
IS fighters took advantage of poor visibility to unleash suicide attackers on SDF forces along the front line in the Euphrates valley late on Sunday, the Syrian Observatory for Human Rights said.
"Twenty-three SDF fighters were killed and nine IS jihadists were also killed in fighting that lasted all night and into Monday morning," Observatory chief Rami Abdel Rahman said.
The SDF launched what is meant to be the final offensive on the jihadist organisation four months ago with air and ground support from coalition forces.
(With inputs from AFP)
The Islamist State could not retain their last bastion in eastern Syria in the fight which also killed 23 members of the US-backed forces.