Defense Secretary Ash Carter Monday hailed the recapture of Manbij, a key strategic town in Syria as "another significant milestone in the campaign to deal ISIL a lasting defeat."

"I want to congratulate the people of Manbij, the Manbij Military Council, the Syrian Arab Coalition and the Syrian Democratic Forces for their success in liberating Manbij city from ISIL's hateful rule," Carter said in a statement released by the Pentagon.

Manbij, a city in Northern Syria, has been under Islamic State control since 2014, and its capture cuts off a primary supply line for the smuggling of fighters and supplies from neighboring Turkey.

"Manbij city was a key transit point for ISIL fighters going into both Syria and Iraq, and for its external operators plotting attacks against our allies, our partners and our homeland," Carter said

The city had been under siege by Syrian Democratic Forces, backed by the U.S., for weeks, and its liberation is seen as a vital step toward facilitating an assault on Raqqa, the Islamic State's de facto capital in Syria, another point underscored in Carter's statement.

"The success in Manbij city will also help reinforce the growing isolation of Raqqa and enable us to achieve the next objective of our campaign in Syria — collapsing ISIL's control over that city."

Carter also expressed appreciation to Turkey, a coalition and NATO ally, thanking it for providing what he called "support to this critical operation."

Relations between the two countries have been strained by Turkey's demand for the extradition of a Muslim cleric, whom Turkish President Recep Tayyip Erdogan accuses of ordering last month's failed coup.

Carter asked for members of the counter-Islamic State coalition to help rebuild Manbij, which has been ravaged by the fighting.

"Now begins the difficult job of rebuilding their homes and communities, and I call on all of our coalition partners to help them with that task," Carter said.

"For its part, the military coalition will continue to work with capable and motivated local forces to defeat ISIL and ensure it remains defeated."