The fighters have cut off all routes into and out of Raqqa, said Nasir Haj Mansour, a senior commander of the Syrian Democratic Forces
-- a mainly Kurdish and Arab coalition.
The SDF launched an offensive to seize the city June 6.
For more than three years, ISIS has used Raqqa as a staging ground for its deadly attacks on the Middle East and further overseas.
Capturing Raqqa would be a major achievement in the battle against ISIS and help bring an end to its brutal experiment of creating an Islamic caliphate.
Nearly 200,000 people and 5,000 militants live in the city, according to the organization Raqqa Is Being Slaughtered Silently.
The bid to retake the Syrian city comes as ISIS faces a likely defeat on another front. Iraqi forces are closing in on completely seizing Mosul
, the terror group's last major stronghold in Iraq.
Col. Ryan Dillon
, a spokesman for the US-led coalition, detailed the SDF's strides to reporters Thursday in the third week of the offensive on Raqqa.
He said the forces have cleared about 7.5 square miles from ISIS in and around the city this week. The SDF now control "all high-speed avenues of approach into Raqqa from the south," Dillon said.
"ISIS fighters, abandoned by their leadership, are being pressured by the SDF from multiple axes around the city," he said.
Elsewhere in Syria, government troops cleared out ISIS fighters from the Rusafa-Athria road area, a stronghold in Aleppo province, the UK-based monitoring group Syrian Observatory for Human Rights said Friday.