The American military’s war on the Islamic State is about to dramatically escalate with a siege of Raqqa, the Syrian city that serves as the de facto capital and chief stronghold of ISIS, according to a U.S. military spokesperson.

Army Col. John Dorrian, the spokesperson for Operation Inherent Resolve, the name given to the mission to defeat ISIS, told reporters in Baghdad that “ultimately we’re isolating Raqqa and we are going to, at a time that our partners choose, move in and liberate that city from” the Islamic State, according to the Associated Press.

The “partners” in this case refer largely to the Syrian Democratic Forces, the U.S.-backed moderate Syrian rebels that have been trained and equipped by the American military. Just this week, Reuters reported that Syrian Democratic Forces advanced to within a mile of a key ISIS stronghold called Tabqa, just 25 miles outside of Raqqa, and repelled and ISIS counterassault in the process.  

“For now, the target in front of our eyes is the city of Tabqa, and the dam,” Gharib Rasho, an official for the Syrian Democratic Forces, told Reuters. Rasho was additionally referring to a nearby dam on the Euphrates River.

The Syrian Democratic Forces’ offensive to retake Raqqa began in November 2016, as part of the strategy to combat the Islamic State outlined by the Obama administration. The Trump administration has yet to unveil a new strategy to defeat ISIS, but the proposal delivered to the administration from the Pentagon last month has been described as an “intensification” of the Obama administration strategy, according to a report from NBC News.  

For now, it remains unclear if the U.S.-supported coalition will continue to advance against ISIS in Syria, and what the specific time table could be for the eventual siege and fall of Raqqa. According to the report from Reuters, it could be a matter of weeks, or a matter of months.