The renewed offensive comes months after the fight against ISIS in eastern Syria stalled after Kurdish fighters from the U.S.-backed Syrian Democratic Forces headed to western Syria to help fight off a Turkish military incursion against other Kurdish forces in Afrin Province.
But with Turkish forces taking Afrin in mid-March, SDF forces have began trickling back to eastern Syria.
“With the return of significant amounts of fighters from the conflict in northern Syria the operations against ISIS in eastern Syria could resume,” said Eric Pahon, a Pentagon spokesman.
U.S. military leaders with the U.S.-led coalition fighting ISIS in Iraq and Syria welcomed the SDF's announcement on Tuesday.
"We continue to stand alongside our partners and ensure the liberation of all terrain held by ISIS terrorists," said Maj. Gen. James Jarrard, commanding general of the Special Operations Joint Task Force-Operation Inherent Resolve. "This is a key milestone in bringing lasting stability to both Iraq and Syria."
The last remaining ISIS fighters in Syria are holed up in an area north of the town of Abu Kamal along the Iraq-Syria border and in the town of Hajin along the eastern side of the Euphrates River.
When the SDF’s land offensive ground to a halt in February, the U.S.-led coalition increased the pace of airstrikes in eastern Syria to keep ISIS at bay in those areas.
Last week, Defense Secretary James Mattis told a congressional committee that he expected the SDF to resume its fight against ISIS soon.
“You’ll see a re-energized effort against the middle Euphrates River Valley in the days ahead and against the rest of the geographic caliphate,” Mattis told the Senate Armed Services Committee.
There are more than 2,000 American troops in eastern Syria assisting and advising the SDF in the fight against ISIS.
President Trump has said that he favors the eventual withdrawal of U.S. troops from Syria.
But at a news conference last week, Trump said the U.S. also wants “to leave a strong and lasting footprint.”
On Monday, Mattis told Pentagon reporters that the pullout of U.S. troops in Syria wouldn’t happen until after diplomatic efforts bring a negotiated end to the civil war.
“We do not want to simply pull out before the diplomats have won the peace,” said Mattis. “So, you win the fight and you win the peace.”